JP4157206B2 - Polypropylene resin foamed particles and molded polypropylene resin foam particles - Google Patents
Polypropylene resin foamed particles and molded polypropylene resin foam particles Download PDFInfo
- Publication number
- JP4157206B2 JP4157206B2 JP34100298A JP34100298A JP4157206B2 JP 4157206 B2 JP4157206 B2 JP 4157206B2 JP 34100298 A JP34100298 A JP 34100298A JP 34100298 A JP34100298 A JP 34100298A JP 4157206 B2 JP4157206 B2 JP 4157206B2
- Authority
- JP
- Japan
- Prior art keywords
- particles
- expanded
- polypropylene resin
- foamed
- resin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明はポリオレフィン系樹脂発泡粒子及びポリプロピレン系樹脂発泡粒子成形体に関する。
【０００２】
【従来の技術】
ポリプロピレン系樹脂発泡粒子を金型内に充填し、スチーム等の熱媒体によって加熱して金型形状通りの発泡成形体を得る型内発泡成形法は、緩衝性、断熱性、機械的物性等の諸物性に優れ、しかも複雑な形状の製品も比較的容易に得ることができ、この方法によって得られた型内発泡成形体は、断熱材や各種製品の緩衝材、包装材等として広く利用されている。
【０００３】
型内発泡成形法において用いるポリプロピレン系樹脂発泡粒子には、金型に充填してスチーム等で加熱した際に、発泡粒子相互の融着性が優れるものであること、得られた成形体を金型から取り出した後に、成形体に生じた収縮の回復性に優れるものであること等の物性が要求される。従来は、融着性、収縮回復性の良好なものを得るために発泡粒子の二次発泡力を高るようにして成形している。そして、発泡粒子の二次発泡力を高める方法として、型内成形用のポリプロピレン系樹脂発泡粒子の基材樹脂として、溶融時の流動性が良好なメルトフローインデックス（ＭＦＩ）が７〜１５ｇ／１０分程度のものを用いることや、発泡粒子を成形する前に発泡粒子を空気等で加圧処理して内圧を高めることが行われている。
【０００４】
また、高発泡倍率の発泡粒子を成形に用いる場合、高発泡倍率の発泡粒子は低発泡倍率のものよりもセル膜強度が弱く、得られた発泡成形体を金型から取り出した後の収縮回復性が特に悪いため、型内発泡成形前に発泡粒子に更に高い内圧を付与したり、金型から取り出した後の発泡成形体の加熱養生を長く行う等の方法が採用されていた。
【０００５】
【発明が解決しようとする課題】
しかしながら、発泡粒子に高い内圧を付与すると、発泡粒子を加熱成形した後に長時間の冷却が必要となり、成形体の熱成形サイクルが長くなるとともに、発泡粒子に内圧を付与するための時間や、得られた発泡成形体の収縮を回復するための養生時間が長くかかり、この結果成形体の製造効率が低下するという問題があった。
【０００６】
本発明者等は上記課題を解決すべく鋭意研究した結果、従来、発泡性が良くないとされていたＭＦＩが低いプロピレン系樹脂の中から特にプロピレン系ランダム共重合体又はランダムブロック共重合体を基材樹脂として用い、且つその樹脂から得られる発泡粒子のＭＦＩ、Ｚ平均分子量、融点及び示差走査熱量測定によって得られるＤＳＣ曲線における吸熱エネルギーを特定の値とすることにより、発泡粒子の二次発泡性が良好で粒子相互の融着性に優れるとともに、熱成形サイクルの短縮、養生時間の短縮を図ることができ、しかも得られた発泡成形体の耐割れ性も向上することができることを見出し本発明を完成するに至った。
【０００７】
【課題を解決するための手段】
即ち本発明のポリプロピレン系樹脂発泡粒子は、加熱成形により相互に融着させて得られるポリプロピレン系樹脂発泡粒子成形体の成形に使用されるプロピレン系ランダム共重合体を基材樹脂とするポリプロピレン系樹脂発泡粒子であって、該発泡粒子から求められるメルトフローインデックスが０．５〜６ｇ／１０分、Ｚ平均分子量（ポリスチレン換算）が１．２×１０６以上、融点が１３０℃以上、示差走査熱量測定によって求められるＤＳＣ曲線（但し、発泡粒子１〜３ｍｇを示差走査熱量計によって１０℃／分の昇温速度で室温から２００℃まで昇温した時に得られるＤＳＣ曲線）に、二つ以上の吸熱ピークが現れ、これらの吸熱ピークのうち固有ピークよりも高温側に現れる吸熱ピークの吸熱エネルギーが５〜１８Ｊ／ｇであることを特徴とする。本発明のポリプロピレン系樹脂発泡粒子において、見かけの密度が０．０１５〜０．０５ｇ／ｃｍ３のものにあっては固有ピークよりも高温側に現れる吸熱ピークの吸熱エネルギーが５〜１８Ｊ／ｇであることが好ましい。
【０００８】
本発明のポリプロピレン系樹脂発泡粒子は、無機ガス系発泡剤によって発泡された発泡粒子であることが好ましい。
【０００９】
また本発明のポリプロピレン系樹脂発泡粒子成形体は、上記ポリプロピレン系樹脂発泡粒子を、加熱成形により相互に融着させて得られる成形体である。
【００１０】
【発明の実施の形態】
本発明において用いる発泡粒子の基材樹脂であるプロピレン系ランダム共重合体、プロピレン系ランダムブロック共重合体のコモノマー成分としては、エチレンや炭素数４〜８のα−オレフィンが挙げられる。基材樹脂の具体例としては、エチレン−プロピレンランダム共重合体、ブテン−プロピレンランダム共重合体、エチレン−ブテン−プロピレンランダム共重合体、エチレン−プロピレンランダムブロック共重合体等が挙げられるが、エチレン−プロピレンランダム共重合体、ブテン−プロピレンランダム共重合体、エチレン−ブテン−プロピレンランダム共重合体が好ましい。
【００１１】
上記プロピレン系ランダム共重合体又はプロピレン系ランダムブロック共重合体は、プロピレン成分含量が８０モル％以上のものが好ましい。上記プロピレン系共重合体は、無架橋のものでも架橋したもでも良いが、無架橋のものが好ましい。
【００１２】
上記プロピレン系共重合体はＭＦＩが６ｇ／１０分以下であることが、該共重合体より得られる発泡粒子のＭＦＩを０．５〜６ｇ／１０分に調整する上で好ましい。
【００１３】
また上記プロピレン系共重合体は、Ｚ平均分子量（ポリスチレン換算）が１．５×１０6 以上であることが、該共重合体より得られる発泡粒子のＺ平均分子量（ポリスチレン換算）を１．２×１０6 以上に調整する上で好ましい。
【００１４】
尚、本発明の発泡粒子の基材樹脂として、上記プロピレン系共重合体に他の樹脂を混合して用いることもできる。上記プロピレン系共重合体と混合して用いられる他の樹脂としては、例えば、上記した以外のポリプロピレン系樹脂、例えばプロピレン単独重合体、エチレン−プロピレンブロック共重合体、ブテン−プロピレンブロック共重合体等や、高密度ポリエチレン、中密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレ、直鎖状超低密度ポリエチレン等のポリエチレン系樹脂、ポリブテン樹脂等が挙げられる。その他、エチレン−プロピレンラバーやスチレン−イソプレン−スチレン共重合体、スチレン−ブタジエン−スチレン共重合体及びそれらの水素添加物等のエラストマーが挙げられる。これらの樹脂やエラストマーは、本発明の目的を阻害しない範囲で基材樹脂中に混合することができるが、前記したプロピレン系共重合体に対する配合割合は、３０重量％未満とすることが好ましい。
【００１５】
本発明の発泡粒子は、例えば上記基材樹脂を押出機内で溶融した後、ストランド状に押し出して水中で急冷し、切断する等の公知の方法で造粒した樹脂粒子に発泡剤を含浸させて発泡することにより得られる。樹脂粒子を造粒する際に、発泡助剤、顔料、充填材、安定剤等の公知の添加剤を添加することができる。
【００１６】
樹脂粒子を発泡させるには、まず、樹脂粒子を密閉容器内の分散媒中に分散させ、加圧、加熱、攪拌しながら、樹脂粒子に発泡剤を含浸させる。次いで、樹脂粒子の軟化点以上の温度に加熱した後、発泡剤を含浸させた発泡性樹脂粒子と分散媒とを容器内より低圧の雰囲気中に放出して発泡を行なう。
【００１７】
樹脂粒子を分散させるための分散媒としては、水、アルコール類、グリコール類、グリセリン等の、樹脂粒子を溶解しないものが使用可能であるが、通常は水が用いられる。
【００１８】
樹脂粒子や発泡剤等を分散媒に分散するに当たって、分散時の加熱やその後の発泡工程における加熱によって樹脂粒子相互が融着するのを防止するために、融着防止剤を分散媒に添加することができる。融着防止剤としては、分散媒に溶解せず、加熱により溶融しないものであれば有機物質、無機物質を問わずいずれも使用できるが、一般的には無機系の融着防止剤が使用される。無機系の融着防止剤としては、マイカ、カオリン、酸化アルミニウム、酸化チタン、水酸化アルミニウム等の粉末が好適である。融着防止剤は、平均粒径が０．０１〜１００μｍのものが用いられ、特に０．１〜３０μｍのものが好ましい。
【００１９】
融着防止剤を使用した場合、分散助剤としてドデシルベンゼンスルホン酸ナトリウム、アルキルスルホン酸ナトリウム、オレイン酸ナトリウム等のアニオン系界面活性剤を併用することが好ましい。融着防止剤は、樹脂粒子１００重量部当たり０．０１〜２重量部添加し、分散助剤は樹脂粒子１００重量部当たり０．００１〜１重量部添加することが好ましい。
【００２０】
樹脂粒子を発泡させるための発泡剤としては、無機ガスや有機発泡剤を用いることができる。無機ガスとしては、二酸化炭素、空気、窒素、ヘリウム、アルゴン等が挙げられる。また、有機発泡剤としては、プロパン、ブタン、ヘキサン等の脂肪族炭化水素類、シクロブタン、シクロヘキサン等の環式脂肪族炭化水素類、クロロジフロロメタン、１−クロロ−１，１−ジフロロエタン、１，１−ジフロロエタン、１，１，１，２−テトラフロロエタン、メチルクロライド、エチルクロライド、メチレンクロライド等のハロゲン化炭化水素類等が挙げられる。
【００２１】
上記発泡剤は、単独で用いても、或いは二種以上を混合して用いてもよい。また、有機発泡剤と無機ガスとを混合して用いることもできる。しかし、有機発泡剤として使用されている化合物には、毒性や可燃性などの危険性を有するものや、オゾン層破壊や環境汚染等を引き起こすものが多く、またこれらの問題を生じにくいものは高価で実用的でないため、これらを考慮すれば無機ガスを用いるのが好ましい。
【００２２】
発泡剤の添加量は、目標とする発泡粒子の発泡倍率に応じて適宜調整するが、基材樹脂の種類、発泡剤の種類等の違いにより、発泡剤の添加量が同じであっても得られる発泡粒子の発泡倍率が同じになるとは限らない。従って、基材樹脂の種類、発泡剤の種類、目標とする発泡倍率等の違いを考慮せずに、発泡剤の好ましい添加量を一律に規定することは困難であるが、一般的には、発泡剤として無機ガスを用いる場合、密閉容器内の平衡蒸気圧が５〜６０ｋｇｆ／ｃｍ2 Ｇ程度となるように添加することが好ましく、発泡剤として有機発泡剤を用いる場合には樹脂粒子１００重量部に対して５〜３０重量部程度となるように添加することが好ましい。
【００２３】
上記のようにして樹脂粒子に発泡剤を含浸させた後、密閉容器の一端を開放して樹脂粒子と分散媒とを容器内よりも低圧の雰囲気下、通常は大気圧下に放出することによって、樹脂粒子を発泡せしめて発泡粒子を得ることができる。上記基材樹脂の一連の発泡操作により樹脂粒子のＭＦＩは高くなり、Ｚ平均分子量は低くなる。これらの変動は主に樹脂粒子を造粒する際に発生すると考えられる。
【００２４】
本発明の発泡粒子から求められるＭＦＩは０．５〜６ｇ／１０分、Ｚ平均分子量は１．２×１０6 以上である。ＭＦＩは基材樹脂から発泡粒子を得る一連の発泡操作において、おおむね、基材樹脂のＭＦＩ（ｇ／１０分）≒発泡粒子から求められるＭＦＩ−（０．１〜３）ｇ／１０分の関係を有することが判っている。またＺ平均分子量（ポリスチレン換算）においても、一連の発泡操作において、おおむね、基材樹脂のＺ平均分子量≒発泡粒子から求められるＺ平均分子量＋（１．０×１０5 〜４．０×１０5 ）の関係があることが経験的に判っており、これらの経験則に基づいて基材樹脂を選択することにより、おおよそ上記ＭＦＩ及びＺ平均分子量を有する発泡粒子を得ることができる。
【００２５】
尚、一連の発泡操作の条件、装置等の相違により上記経験則が適用できない場合は、その場合に適合する経験則を見出し、新たに見出した経験則に基づいて基材樹脂を選択し、本発明で特定するＭＦＩ及びＺ平均分子量を満足する発泡粒子を得ることができる。本発明発泡粒子において、ＭＦＩが６ｇ／１０分を超える場合、発泡粒子の気泡が微細化したり、連続気泡構造となり易く、また発泡粒子のセル膜強度も弱くなるという問題を生じる。一方、ＭＦＩが０．５ｇ／１０分未満であると、後述の各条件を満たしていても、発泡粒子の二次発泡性が低下し、良好な型内成形体を得ることができなくなる。上記ポリプロピレン系共重合体のＭＦＲは、好ましくは２〜５．５ｇ／１０分である。またＺ平均分子量（ポリスチレン換算）が１．２×１０6 未満の場合には、樹脂剛性が低く、発泡粒子のセル膜強度が弱くなる。上記Ｚ平均分子量は好ましくは１．３×１０６以上、より好ましくは１．３×１０６〜２．５×１０６である。また本発明の発泡粒子は、示差走査熱量測定によって求められるＤＳＣ曲線（但し、発泡粒子１〜３ｍｇを示差走査熱量計によって１０℃／分の昇温速度で室温から２００℃まで昇温した時に得られるＤＳＣ曲線）に、二つ以上の吸熱ピークが現れ、これら吸熱ピークのうち固有ピークよりも高温側に現れる一つ以上の吸熱ピーク（以下、単に高温ピークと言う。）の吸熱エネルギーが５〜１８Ｊ／ｇとなる結晶構造を有する。
尚、高温ピークの吸熱エネルギーは、固有ピークよりも高温側に現れる１つ以上の吸熱ピーク全ての吸熱エネルギーの合計を意味するものであり、固有ピークよりも高温側に現れる個々の吸熱ピークにおいて常に本発明にて特定する値を満足しなければならないことを意味するものではない。
【００２６】
ＤＳＣ曲線に二つ以上の吸熱ピークが現れ、且つ高温ピークの吸熱エネルギーが１〜２０Ｊ／ｇである発泡粒子は、上記樹脂粒子を発泡させる際の発泡（放出時の）温度、発泡前に密閉容器内で樹脂粒子を発泡温度より数℃低い温度に保持する際の温度、時間の条件等を制御することにより得られる。発泡粒子の高温ピークの吸熱エネルギーが２０Ｊ／ｇを超える場合、樹脂粒子から発泡粒子を得る際に発泡性が低い。また成形時における発泡粒子の二次発泡性が低く、発泡粒子の融着不良を生じ、外観や物性の良好な成形体が得られない。また高温ピークの吸熱エネルギーが１Ｊ／ｇ未満の発泡粒子は、連続気泡率が高くなり、発泡成形体の収縮回復不良を生じたり、成形体の諸物性の低下をきたす虞れがある。また、本発明の発泡粒子から求められる融点は１３０℃以上であることが必要である。融点が１３０℃未満であるとポリプロピレン系樹脂の特性が発揮されにくくなり、ポリエチレン系樹脂に近い性状を示すようになる。また融点は、発泡粒子の型内発泡成形性の面から、好ましくは１３５〜１５５℃、更に好ましくは１３５〜１５０℃である。尚、発泡粒子から求められる融点は、後述する融点の測定方法を適用して求められる基材樹脂の融点とほぼ同じであるため、発泡粒子から求められる融点の調整は基材樹脂の融点を調整すれば良い。
【００２７】
樹脂粒子を発泡させるために用いる発泡剤として従来公知のものが使用できるが、無機ガス系発泡剤を用いると高温ピークの吸熱エネルギーを１〜２０Ｊ／ｇに調整するための条件の制御が容易であり、この点からも発泡剤としては無機ガス系が好ましい。尚、無機ガス系発泡剤としては、二酸化炭素、窒素、空気、水から選択される一種以上のもの、更にそれらにブタン等の有機発泡剤を発泡剤全量に対して５０重量％以下混合したものが含まれる。
【００２８】
無機ガス系発泡剤を使用する上記方法によれば、見かけの密度が０．０２〜０．８ｇ／ｃｍ3 の良好な発泡粒子を得ることができるが、より低密度の発泡粒子を得るには、上記のようにして得た発泡粒子（以下、便宜的に一段発泡粒子と呼ぶ。）を再度発泡させる方法（二段発泡法。二段発泡法によって得た発泡粒子を二段発泡粒子と呼ぶ。）が採用される。二段発泡粒子は、一段発泡粒子を密閉容器内に入れて無機ガス等によって加圧処理して発泡粒子内の圧力を常圧よりも高くした後、該発泡粒子をスチーム等で加熱して更に発泡させる等の方法により得ることができる。
【００２９】
本発明の発泡粒子を得る方法としては、上記した方法の他に、基材樹脂を発泡剤とともに押出機内で溶融混練した後、ストランド状に押出発泡し、これを切断して発泡粒子とする方法や、基材樹脂に発泡剤を含浸させて発泡性樹脂粒子とした後、加熱して発泡させる方法等、公知の方法を採用することができる。
【００３０】
本発明の発泡粒子のうち、二段発泡法の操作を一回以上行って得られた多段発泡粒子は、見かけの密度が０．０１５〜０．０５ｇ／ｃｍ3 で、高温ピークの吸熱エネルギーが５〜１８Ｊ／ｇのものが好ましい。見かけの密度が０．０１５ｇ／ｃｍ3 未満の場合は、連続気泡率が高くなり易く、その場合、発泡粒子成形体の収縮回復不良、寸法不良を生じ易い。一方、見かけの密度が０．０５ｇ／ｃｍ3 を超える場合は一段発泡法により発泡粒子を得る方が効率的である。また高温ピークの吸熱エネルギーが５Ｊ／ｇ未満の場合は連続気泡率が高くなり、発泡粒子成形体の収縮回復不良を生じたり、成形体の物性低下の虞れがある。一方、高温ピークの吸熱エネルギーが１８Ｊ／ｇを超える場合には、成形時における発泡粒子の二次発泡性が低く、発泡粒子の融着不良を生じ良好な成形体が得られなくなる虞れがある。
【００３１】
上記発泡粒子の見かけの密度は次のようにして求めることができる。即ち、見かけの密度を求めようとする発泡粒子群から約５０００個の発泡粒子をサンプリングし（サンプルの発泡粒子群と呼ぶ。）、このサンプルの発泡粒子群全体の重量：Ｗ（ｇ）を測定した後、メスシリンダー内のエタノール中に沈め、エタノールの水位上昇分よりサンプルの発泡粒子群の体積：Ｌ（ｃｍ3 ）を測定し、サンプルの発泡粒子群の見かけの密度を次式より求める。
【００３２】
【数１】
サンプルの発泡粒子群の見かけの密度（ｇ／ｃｍ3 ）＝Ｗ÷Ｌ
【００３３】
上記本発明の発泡粒子は、金型内に充填して水蒸気などで加熱することにより、発泡粒子が相互に融着して所望の形状に形成された成形体を得ることができる。また、発泡粒子の加熱成形は上記方法に限らず、特開平９−１０４０２６号公報等に記載されるような無端走行する上下のベルト間に発泡粒子を挟んで水蒸気などで加熱することにより発泡粒子を相互に融着させて成形体を得る連続成形方法を採用することもできる。発泡粒子を成形するに先立って、必要に応じて発泡粒子を空気等で加圧して発泡粒子内の圧力を常圧よりも高くしておいても良いが、特に発泡粒子として見かけの密度が０．０１５〜０．０５ｇ／ｃｍ3 、高温ピークの吸熱エネルギーが５〜１２Ｊ／ｇのものを成形に用いる場合、無加圧成形（発泡粒子を常圧より高圧な密閉容器等の加圧系に保持し該粒子内の圧力を高める加圧処理をしていない発泡粒子を金型内に充填して加熱成形して成形体を得る成形）が可能であり、無加圧成形によっても二次発泡性に優れ、粒子相互の融着性に優れた発泡成形体を得ることができるため、無加圧成形用の発泡粒子として好ましい。また、融点、ＭＦＩ、Ｚ平均分子量の条件を満足する見かけの密度が０．０１５〜０．０５ｇ／ｃｍ3 、高温ピークの吸熱エネルギーが５〜１２Ｊ／ｇの上記発泡粒子から成形される、密度０．０１〜０．０３ｇ／ｃｍ3 、高温ピークの吸熱エネルギーが５〜１２Ｊ／ｇの発泡粒子成形体は、低密度のものにもかかわらず寸法安定性、外観、耐割れ性に優れたものであるため特に好ましい。
【００３４】
尚、発泡粒子成形体の密度は、発泡粒子成形体からサンプルを切り出し（縦約５ｃｍ、横約５ｃｍ、厚み約５ｃｍのサンプルが好ましい。）、サンプルの重量（ｇ）をサンプルの外形寸法から求められる体積（ｃｍ3 ）で割ることにより求める。
【００３５】
また、発泡粒子を発泡粒子成形体に成形しても、融点、ＭＦＩ及びＺ平均分子量はほとんど変化しないため、発泡粒子と成形体の融点、ＭＦＩ及びＺ平均分子量はほぼ同じ値を示す。
以下、本明細書における融点、発泡粒子及び発泡成形体のＭＦＩ、Ｚ平均分子量及び高温ピークの吸熱エネルギーの測定方法について説明する。
【００３６】
発泡粒子及び発泡成形体の高温ピークの吸熱エネルギーは、例えば図１に示すＤＳＣ曲線において、固有ピークａよりも高温側に現れる高温ピークｂの面積に相当し、次のようにして求めることができる。まず図１に示すようにＤＳＣ曲線上の８０℃の点Ｉと、ＤＳＣ曲線上の融解終了温度を示す点IIとを結ぶ直線を引く。次に固有ピークａと高温ピークｂ（固有ピークよりも高温側に現れる吸熱ピークの内、最も低温側に存在する吸熱ピーク）との間の谷部にあたるＤＳＣ曲線上の点III を通りグラフ横軸の温度に対して垂直な直線と、点I と点IIとを結んだ直線との交点を点IVとする。このようにして求めた点IVと点IIとを結ぶ直線、点III と点IVを結ぶ直線及び点III と点IIを結ぶＤＳＣ曲線によって囲まれる部分（斜線部分）の面積が高温ピークの吸熱エネルギーに相当する。上記高温ピークｂは、上記のようにして第一回目のＤＳＣ曲線を求めた後、１０℃／分で室温まで降温し、再び１０℃／分で２００℃まで昇温して得た第二回目のＤＳＣ曲線には現れないが、固有ピークは、第一回目のＤＳＣ曲線にも第二回目のＤＳＣ曲線にも現れる。
尚、上記第二回目のＤＳＣ曲線の固有ピークの頂点が示すグラフ横軸上の温度を融点とする。
【００３７】
また、発泡粒子及び発泡粒子成形体のＭＦＩは、発泡粒子、発泡粒子成形体のそれぞれを、１９０℃の加熱プレスにより剪断力が極力作用しないように脱泡せしめて非発泡樹脂板を作成し、該樹脂板よりカッター刃等により測定用小片サンプルを切り出す。得られたサンプルからＪＩＳ Ｋ７２１０（１９９５）表１：条件１４にて求める。
【００３８】
また、発泡粒子及び発泡粒子成形体のＺ平均分子量（ポリスチレン換算）は、下記条件にて求める。
平均分子量測定条件
測定装置：ＷＡＴＥＲＳ社製１５０Ｃ
カラム ：ＴＳＫ−ＧＥＬＧＭＨ６−ＨＴ（東ソー株式会社製）
測定試料：０．４ｍｌ
溶媒 ：オルトジクロルベンゼン（ＯＤＣＢ）
測定温度：１３５℃
流動相 ：ＯＤＣＢ
流動速度：１ｍｌ／ｍｉｎ．
試料濃度：０．２％
【００３９】
【実施例】
次に、具体的実施例を挙げて本発明を詳細に説明する。
実施例１〜９、比較例１〜２
まず、表１に示すプロピレン系共重合体を押出機内で溶融した後、押出機からストランド状に押出し、このストランドを冷却後切断して、重量約１．８ｍｇの樹脂粒子を作製した。
【００４０】
【表１】
次いで４００リットルのオートクレーブ内に、上記樹脂粒子１００ｋｇ、水２３０リットル、分散剤（カオリン）４００ｇ、ドデシルベンゼンスルホン酸ナトリウム２０重量％水溶液（ネオゲンＳ−２０）３０ｇ、及び発泡剤として二酸化炭素を仕込み、表２に示す一段保持温度で保持し、次いで二段保持温度に保持した後、オートクレーブ内を二段保持温度に保持しながらオートクレーブ内容物を大気圧下に放出した。尚、二酸化炭素は放出時のオートクレーブ内圧力が表２に示す圧力となるように供給し、オートクレーブ内容物を放出している間も、同圧力が保持されるようにオートクレーブ内に連続して供給した。得られた発泡粒子（一段発泡粒子）の見かけの密度及び高温ピークの吸熱エネルギーを表２に示す。次いで、一段発泡粒子を空気で加圧処理し、表３に示す内圧を付与した後、同表に示す圧力のスチームで加熱して再度発泡させ二段発泡粒子を得た。得られた二段発泡粒子の性状を表３に示す。
【００４２】
【表２】
【表３】
上記のようにして得た発泡粒子（二段発泡粒子）を、２３℃、大気圧下で２４時間養生した後、実施例１〜７及び比較例１〜２では空気で発泡粒子を加圧処理して１．０ｋｇ／ｃｍ３Ｇの粒子内圧を付与した後、実施例８、９では発泡粒子を加圧処理せずに（粒子内圧力は０ｋｇ／ｃｍ３Ｇ）、平板成形用金型（２５０ｍｍ×２００ｍｍ×５０ｍｍ）内に充填し、表４に示す圧力のスチームで加熱して成形した。金型を型締めしてから発泡粒子を金型内に充填し、次いでスチームで加熱した後、冷却して金型から成形体を取り出すまでの時間を成形サイクルとして表４に示す。
【００４５】
得られた成形体を大気圧下で６０℃で８時間養生した後、成形体の諸物性を測定した。結果を表４にあわせて示す。尚、発泡粒子成形体の融点、ＭＦＩ、Ｚ平均分子量及び高温ピークの吸熱エネルギーは、表３の二段発泡粒子の示す値と同様であった。
【００４６】
【表４】
※１ 表面平滑性は、成形体表面を観察し、
○・・・・表面平滑で凹凸、しわが少ない。
×・・・・表面平滑性に劣り、凹凸、しわが多い。
として評価した。
【００４８】
※２ 収縮回復性は、養生後の成形体縦、横各々の中心線上の長さを測定し、金型寸法に対する収縮率を求め、
○・・・・縦、横の収縮率が５％以下である。
×・・・・少なくとも縦、横どちらか一方の収縮率が５％を超えている。
として評価した。
【００４９】
※３ 融着性は、成形体を長さ１５０ｍｍ、幅５０ｍｍ、厚さ１０ｍｍに切り取った試験片を、引張試験機によって５００ｍｍ／分の速度で引っ張って破断させ、その破断面を観察して、
○・・・・破断面の６０％以上が材料破壊している。
×・・・・破断面の６０％未満が材料破壊している。
として評価した。
【００５０】
※４ 引張強度、引張伸びは、ＪＩＳ Ｋ６７６７に準拠して測定した。
【００５１】
【発明の効果】
以上説明したように、本発明のポリプロピレン系樹脂発泡粒子は、従来発泡性が低いとされていた、低いＭＦＩの基材樹脂を用いていながら、特定のプロピレン系ランダム共重合体又はプロピレン系ランダムブロック共重合体を基材樹脂として用い、且つ融点、ＭＦＩ、Ｚ平均分子量及び発泡粒子の示差走査熱量測定によって得られるＤＳＣ曲線における高温ピークの吸熱エネルギーが特定の値を有する発泡粒子としたことにより、二次発泡性に優れ発泡粒子相互の融着性に優れた発泡成形体を得ることができる。また本発明の発泡粒子は、発泡粒子内の圧力を高く調整しなくても良好な成形を可能とするものであり、そのことにより発泡粒子内の圧力を高く調整したものに比べて金型に充填して加熱成形した後の冷却時間が短くて済み、成形サイクルの短縮化を図ることができるとともに、得られた発泡成形体の収縮回復のための養生時間も短くて済むため、発泡成形体の製造効率を著しく向上させることができる。
【００５２】
また見かけの密度が０．０１５〜０．０５ｇ／ｃｍ3 で、高温ピークの吸熱エネルギーが５〜１２Ｊ／ｇの発泡粒子は、無加圧成形によっても優れた発泡粒子成形体を得ることができ、成形前の発泡粒子への加圧処理工程が省略できるとともに、この無加圧成形により、成形後の冷却時間や成形体の養生時間が更に短くて済むという特有の効果を有し、成形体の製造効率を更に向上させることができる。
【００５３】
更に、本発明の発泡粒子から得た成形体は、発泡粒子相互間の融着性に優れ、耐割れ性に優れるという利点を有する。
【図面の簡単な説明】
【図１】発泡粒子のＤＳＣ曲線の一例を示し、高温ピークの吸熱エネルギーの測定方法の説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyolefin resin expanded particle and a polypropylene resin expanded particle molded body.
[0002]
[Prior art]
The in-mold foam molding method in which polypropylene resin foam particles are filled into a mold and heated by a heat medium such as steam to obtain a foam molded body according to the shape of the mold includes buffering properties, heat insulation properties, mechanical properties, etc. Products with excellent physical properties and complex shapes can be obtained relatively easily, and in-mold foam molded products obtained by this method are widely used as insulation materials, cushioning materials for various products, packaging materials, etc. ing.
[0003]
The polypropylene resin foam particles used in the in-mold foam molding method have excellent fusion properties between the foam particles when filled in a mold and heated with steam or the like. After taking out from the mold, physical properties such as excellent recovery from shrinkage generated in the molded body are required. Conventionally, in order to obtain a material with good fusion property and shrinkage recovery property, molding is performed such that the secondary foaming force of the foamed particles is increased. As a method for increasing the secondary foaming power of the foamed particles, the melt flow index (MFI) having good fluidity at the time of melting is 7 to 15 g / 10 as the base resin of the polypropylene resin foamed particles for in-mold molding. It has been practiced to use about a minute amount or to increase the internal pressure by pressurizing the expanded particles with air or the like before forming the expanded particles.
[0004]
In addition, when foamed particles with a high expansion ratio are used for molding, the expanded foam particles with a high expansion ratio have a weaker cell membrane strength than those with a low expansion ratio, and shrinkage recovery after taking out the obtained foamed molded product from the mold Since the properties are particularly bad, methods such as applying a higher internal pressure to the foamed particles before in-mold foam molding, or subjecting the foam molded body to heat curing after taking out from the mold have been adopted.
[0005]
[Problems to be solved by the invention]
However, when a high internal pressure is applied to the foamed particles, it is necessary to cool the foamed particles for a long time after thermoforming the foamed particles, and the thermoforming cycle of the molded body becomes long. There was a problem that it took a long time to recover the shrinkage of the foamed molded article, and as a result, the production efficiency of the molded article was lowered.
[0006]
As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention selected propylene-based random copolymers or random block copolymers from propylene-based resins having low MFI, which had been considered to have poor foamability. Secondary foaming of foamed particles by using the MFI, Z-average molecular weight, melting point and endothermic energy in the DSC curve obtained by differential scanning calorimetry as a specific value, as a base resin. It has been found that it has excellent properties and excellent fusion between particles, can shorten the thermoforming cycle and shorten the curing time, and can also improve the crack resistance of the obtained foamed molded product. The invention has been completed.
[0007]
[Means for Solving the Problems]
That is, the polypropylene resin expanded particles of the present invention are propylene random copolymers used for forming polypropylene resin expanded particles obtained by fusing each other by thermoforming.BodyPolypropylene resin foamed particles used as a base resin, the melt flow index calculated from the foamed particles is 0.5 to 6 g / 10 min, and the Z average molecular weight (polystyrene conversion) is 1.2 × 106The DSC curve obtained by differential scanning calorimetry with a melting point of 130 ° C. or higher (provided when 1 to 3 mg of foamed particles are heated from room temperature to 200 ° C. at a heating rate of 10 ° C./min with a differential scanning calorimeter. DSC curve) shows two or more endothermic peaks, and among these endothermic peaks, the endothermic energy of the endothermic peak appearing on the higher temperature side than the intrinsic peak is5~18It is characterized by being J / g. In the expanded polypropylene resin particles of the present invention, the apparent density is 0.015 to 0.05 g / cm.3It is preferable that the endothermic energy of the endothermic peak appearing on the higher temperature side than the intrinsic peak is 5 to 18 J / g.
[0008]
The expanded polypropylene resin particles of the present invention are preferably expanded particles expanded with an inorganic gas-based foaming agent.
[0009]
The polypropylene resin of the present inventionFoam particlesThe molded body isthe aboveObtained by fusing polypropylene resin expanded particles to each other by thermoformingRuFormIt is.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the comonomer component of the propylene-based random copolymer and propylene-based random block copolymer that are the base resin of the expanded particles used in the present invention include ethylene and α-olefins having 4 to 8 carbon atoms. Specific examples of the base resin include ethylene-propylene random copolymer, butene-propylene random copolymer, ethylene-butene-propylene random copolymer, ethylene-propylene random block copolymer, and the like. -Propylene random copolymer, butene-propylene random copolymer, ethylene-butene-propylene random copolymer are preferable.
[0011]
The propylene random copolymer or propylene random block copolymer preferably has a propylene component content of 80 mol% or more. The propylene-based copolymer may be non-crosslinked or crosslinked, but is preferably non-crosslinked.
[0012]
The propylene-based copolymer preferably has an MFI of 6 g / 10 min or less in order to adjust the MFI of the expanded particles obtained from the copolymer to 0.5 to 6 g / 10 min.
[0013]
The propylene-based copolymer has a Z-average molecular weight (polystyrene conversion) of 1.5 × 106That is the above, the Z average molecular weight (polystyrene conversion) of the expanded particles obtained from the copolymer is 1.2 × 106It is preferable in adjusting above.
[0014]
In addition, as the base resin for the expanded particles of the present invention, other resins can be mixed with the propylene-based copolymer. Examples of other resins used by mixing with the propylene copolymer include, for example, polypropylene resins other than those described above, such as propylene homopolymers, ethylene-propylene block copolymers, butene-propylene block copolymers, and the like. And polyethylene resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and linear ultra-low-density polyethylene, and polybutene resins. Other examples include elastomers such as ethylene-propylene rubber, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, and hydrogenated products thereof. These resins and elastomers can be mixed in the base resin as long as the object of the present invention is not impaired, but the blending ratio with respect to the propylene-based copolymer is preferably less than 30% by weight.
[0015]
For example, the foamed particles of the present invention are obtained by impregnating a foaming agent with resin particles granulated by a known method such as melting the base resin in an extruder, extruding it into a strand, quenching in water, and cutting. Obtained by foaming. When granulating the resin particles, known additives such as foaming aids, pigments, fillers and stabilizers can be added.
[0016]
In order to foam the resin particles, first, the resin particles are dispersed in a dispersion medium in a sealed container, and the resin particles are impregnated with a foaming agent while being pressurized, heated, and stirred. Next, after heating to a temperature equal to or higher than the softening point of the resin particles, the foamable resin particles impregnated with the foaming agent and the dispersion medium are discharged into a low-pressure atmosphere from the inside of the container to perform foaming.
[0017]
As the dispersion medium for dispersing the resin particles, water, alcohols, glycols, glycerin and the like that do not dissolve the resin particles can be used, but water is usually used.
[0018]
When dispersing resin particles, foaming agents, etc. in the dispersion medium, an anti-fusion agent is added to the dispersion medium in order to prevent the resin particles from being fused together by heating during dispersion or heating in the subsequent foaming step. be able to. As the anti-fusing agent, any organic or inorganic substance can be used as long as it does not dissolve in the dispersion medium and does not melt by heating. Generally, an inorganic anti-fusing agent is used. The As the inorganic anti-fusing agent, powders such as mica, kaolin, aluminum oxide, titanium oxide, and aluminum hydroxide are suitable. As the anti-fusing agent, those having an average particle diameter of 0.01 to 100 μm are used, and those having an average particle diameter of 0.1 to 30 μm are particularly preferable.
[0019]
When an anti-fusing agent is used, it is preferable to use an anionic surfactant such as sodium dodecylbenzene sulfonate, sodium alkyl sulfonate, or sodium oleate as a dispersion aid. It is preferable to add 0.01 to 2 parts by weight of the anti-fusing agent per 100 parts by weight of the resin particles and 0.001 to 1 parts by weight of the dispersion aid per 100 parts by weight of the resin particles.
[0020]
As a foaming agent for foaming the resin particles, an inorganic gas or an organic foaming agent can be used. Examples of the inorganic gas include carbon dioxide, air, nitrogen, helium, and argon. Examples of the organic blowing agent include aliphatic hydrocarbons such as propane, butane and hexane, cyclic aliphatic hydrocarbons such as cyclobutane and cyclohexane, chlorodifluoromethane, 1-chloro-1,1-difluoroethane, 1 , 1-difluoroethane, 1,1,1,2-tetrafluoroethane, halogenated hydrocarbons such as methyl chloride, ethyl chloride, methylene chloride, and the like.
[0021]
The said foaming agent may be used independently, or may mix and use 2 or more types. Moreover, an organic foaming agent and inorganic gas can also be mixed and used. However, many compounds used as organic foaming agents have dangers such as toxicity and flammability, and those that cause ozone layer destruction and environmental pollution, and those that do not easily cause these problems are expensive. In view of these, it is preferable to use an inorganic gas.
[0022]
The amount of foaming agent added is appropriately adjusted according to the target foaming ratio of the foamed particles, but it can be obtained even if the amount of foaming agent added is the same due to differences in the types of base resin and foaming agent. The expansion ratio of the expanded particles to be produced is not necessarily the same. Therefore, it is difficult to uniformly define the preferred addition amount of the foaming agent without considering the difference in the type of base resin, the type of foaming agent, the target expansion ratio, etc. When inorganic gas is used as the blowing agent, the equilibrium vapor pressure in the sealed container is 5 to 60 kgf / cm.2It is preferable to add so that it may become about G, and when using an organic foaming agent as a foaming agent, it is preferable to add so that it may become about 5-30 weight part with respect to 100 weight part of resin particles.
[0023]
After impregnating the resin particles with the foaming agent as described above, one end of the sealed container is opened, and the resin particles and the dispersion medium are released in an atmosphere at a lower pressure than the inside of the container, usually under atmospheric pressure. The foamed particles can be obtained by foaming the resin particles. By a series of foaming operations of the base resin, the MFI of the resin particles increases and the Z average molecular weight decreases. These fluctuations are considered to occur mainly when the resin particles are granulated.
[0024]
MFI calculated | required from the expanded particle of this invention is 0.5-6 g / 10min, Z average molecular weight is 1.2 * 10.6That's it. MFI is a series of foaming operations for obtaining expanded particles from a base resin. In general, MFI of base resin (g / 10 min) ≈MFI required from expanded particles- (0.1-3) g / 10 min. Is known to have Also in terms of the Z average molecular weight (polystyrene conversion), in a series of foaming operations, the Z average molecular weight of the base resin is generally calculated from the Z average molecular weight of the base resin + (1.0 × 10 × 10).Five~ 4.0 × 10Five) Is empirically known, and by selecting a base resin based on these empirical rules, expanded particles having approximately the above MFI and Z average molecular weight can be obtained.
[0025]
If the above empirical rule cannot be applied due to differences in the series of foaming operation conditions, equipment, etc., find an empirical rule that matches that case, select the base resin based on the newly found empirical rule, Expanded particles satisfying the MFI and Z average molecular weight specified in the invention can be obtained. When the MFI exceeds 6 g / 10 min in the foamed particles of the present invention, there arises a problem that the foamed bubbles tend to be finer or have an open cell structure, and the cell membrane strength of the foamed particles is weakened. On the other hand, if the MFI is less than 0.5 g / 10 minutes, the secondary foamability of the foamed particles is lowered even when the following conditions are satisfied, and a good in-mold product cannot be obtained. The MFR of the polypropylene copolymer is preferably 2 to 5.5 g / 10 minutes. Moreover, Z average molecular weight (polystyrene conversion) is 1.2 × 106 If it is less than 1, the resin rigidity is low, and the cell membrane strength of the expanded particles becomes weak. The Z average molecular weight is preferably 1.3 × 106Or more, more preferably 1.3 × 106~ 2.5 × 106It is. The expanded particles of the present invention are obtained when the DSC curve obtained by differential scanning calorimetry (however, 1 to 3 mg of expanded particles are heated from room temperature to 200 ° C. at a temperature increase rate of 10 ° C./min with a differential scanning calorimeter. Two or more endothermic peaks appear in the DSC curve), and the endothermic energy of one or more endothermic peaks (hereinafter simply referred to as the high temperature peak) appearing on the higher temperature side than the intrinsic peak among these endothermic peaks.5~18It has a crystal structure of J / g.
The endothermic energy of the high temperature peak means the sum of the endothermic energies of all one or more endothermic peaks that appear on the higher temperature side than the intrinsic peak, and is always the individual endothermic peak that appears on the higher temperature side than the intrinsic peak. It does not mean that the values specified in the present invention must be satisfied.
[0026]
Two or more endothermic peaks appear in the DSC curve, and the expanded particles having an endothermic energy of 1-20 J / g at the high temperature peak are sealed before foaming. In the containerresinIt is obtained by controlling the temperature, time conditions, etc. when holding the particles at a temperature several degrees lower than the foaming temperature.ThisThe When the endothermic energy at the high temperature peak of the expanded particles exceeds 20 J / g, the expandability is low when the expanded particles are obtained from the resin particles. Further, the secondary foamability of the foamed particles at the time of molding is low, resulting in poor fusion of the foamed particles, and a molded article having good appearance and physical properties cannot be obtained. In addition, the expanded particles having a high temperature peak endothermic energy of less than 1 J / g have a high open cell ratio, which may cause a shrinkage recovery failure of the foamed molded product or may deteriorate various physical properties of the molded product. In addition, the melting point required from the expanded particles of the present invention needs to be 130 ° C. or higher. When the melting point is less than 130 ° C., the properties of the polypropylene resin are hardly exhibited, and the properties close to those of the polyethylene resin are exhibited. The melting point is preferably 135 to 155 ° C, more preferably 135 to 150 ° C, from the viewpoint of in-mold foam moldability of the expanded particles. In addition, since the melting point calculated | required from expanded particle is substantially the same as the melting point of base resin calculated | required by applying the measuring method of melting point mentioned later, adjustment of melting | fusing point calculated | required from expanded particle adjusts melting | fusing point of base resin Just do it.
[0027]
Conventionally known foaming agents can be used for foaming the resin particles. However, when an inorganic gas foaming agent is used, it is easy to control conditions for adjusting the endothermic energy of the high temperature peak to 1 to 20 J / g. From this point, an inorganic gas system is preferable as the foaming agent. The inorganic gas-based foaming agent is one or more selected from carbon dioxide, nitrogen, air, and water, and further mixed with an organic foaming agent such as butane in an amount of 50% by weight or less based on the total amount of the foaming agent. Is included.
[0028]
According to the above method using an inorganic gas-based blowing agent, the apparent density is 0.02 to 0.8 g / cm.ThreeHowever, in order to obtain lower density expanded particles, the expanded particles obtained as described above (hereinafter referred to as single-stage expanded particles for convenience) are expanded again. (Two-stage foaming method. Foamed particles obtained by the two-stage foaming method are referred to as two-stage foamed particles). The two-stage expanded particles are obtained by placing the first-stage expanded particles in a closed container and pressurizing with an inorganic gas to increase the pressure in the expanded particles above normal pressure, and then heating the expanded particles with steam or the like. It can be obtained by a method such as foaming.
[0029]
As a method for obtaining the expanded particles of the present invention, in addition to the above-described method, a base resin is melt-kneaded in an extruder together with a foaming agent, and then extruded and foamed into a strand shape, which is cut to obtain expanded particles. Alternatively, a known method such as a method in which a base resin is impregnated with a foaming agent to form foamable resin particles and then heated to foam can be employed.
[0030]
Among the expanded particles of the present invention, the multistage expanded particles obtained by performing the operation of the two-stage expansion method one or more times have an apparent density of 0.015 to 0.05 g / cm.ThreeAnd the thing of 5-18 J / g of endothermic energy of a high temperature peak is preferable. Apparent density of 0.015 g / cmThreeIf the ratio is less than 1, the open cell ratio tends to be high, and in that case, shrinkage recovery failure and dimensional failure of the foamed particle molded body are likely to occur. On the other hand, the apparent density is 0.05 g / cmThreeIn the case of exceeding 1, it is more efficient to obtain expanded particles by a single-stage expansion method. On the other hand, when the endothermic energy at the high temperature peak is less than 5 J / g, the open cell ratio is increased, and there is a possibility that the shrinkage recovery failure of the foamed particle molded body may occur or the physical properties of the molded body may be lowered. On the other hand, when the endothermic energy at the high temperature peak exceeds 18 J / g, the secondary foamability of the foamed particles at the time of molding is low, which may cause poor fusion of the foamed particles and a good molded product may not be obtained. .
[0031]
The apparent density of the expanded particles can be determined as follows. That is, about 5000 expanded particles are sampled from the expanded particle group whose apparent density is to be obtained (referred to as the expanded particle group of the sample), and the weight: W (g) of the entire expanded particle group of the sample is measured. After that, the sample was submerged in ethanol in a graduated cylinder, and the volume of the foamed particle group of the sample: L (cmThree) And the apparent density of the foamed particle group of the sample is obtained from the following equation.
[0032]
[Expression 1]
Apparent density of the foam particles of the sample (g / cmThree) = W ÷ L
[0033]
The foamed particles of the present invention are filled in a mold and heated with water vapor or the like to obtain a molded body in which the foamed particles are fused to each other and formed into a desired shape. In addition, the thermoforming of the foamed particles is not limited to the above method, and the foamed particles are heated by steaming with the foamed particles sandwiched between upper and lower belts that run endlessly as described in JP-A-9-104026. It is also possible to employ a continuous molding method in which the molded bodies are obtained by fusing the two together. Prior to molding the foamed particles, the foamed particles may be pressurized with air or the like as necessary to increase the pressure inside the foamed particles to be higher than the normal pressure. .015 to 0.05 g / cmThree, When a high-temperature peak endothermic energy of 5 to 12 J / g is used for molding, pressureless molding (the foamed particles are held in a pressurized system such as a sealed container higher than normal pressure to increase the pressure in the particles) It is possible to mold foamed particles that have not been pressure-treated in a mold and heat-molded to obtain a molded product). Therefore, it is preferable as expanded particles for pressureless molding. The apparent density satisfying the conditions of melting point, MFI, and Z average molecular weight is 0.015 to 0.05 g / cm.ThreeThe density is 0.01 to 0.03 g / cm, which is molded from the above expanded particles having a high temperature peak endothermic energy of 5 to 12 J / g.ThreeA foamed particle molded body having an endothermic energy of 5-12 J / g at a high temperature peak is particularly preferable because it has excellent dimensional stability, appearance, and crack resistance despite its low density.
[0034]
The density of the foamed particle molded body is determined by cutting a sample from the foamed particle molded body (preferably a sample having a length of about 5 cm, a width of about 5 cm, and a thickness of about 5 cm), and obtaining the weight (g) of the sample from the outer dimensions of the sample. Volume (cm)Three) Divided by
[0035]
Further, even when the foamed particles are molded into a foamed particle molded body, the melting point, MFI, and Z average molecular weight hardly change. Therefore, the melting point, MFI, and Z average molecular weight of the foamed particles and the molded body show substantially the same values.
Hereinafter, the measuring method of melting | fusing point in this specification, MFI of a foaming particle and a foaming molding, Z average molecular weight, and the endothermic energy of a high temperature peak is demonstrated.
[0036]
The endothermic energy of the high temperature peak of the expanded particles and the expanded molded body corresponds to the area of the high temperature peak b appearing on the higher temperature side than the intrinsic peak a in the DSC curve shown in FIG. 1, for example, and can be obtained as follows. . First, as shown in FIG. 1, a straight line connecting a point I of 80 ° C. on the DSC curve and a point II indicating the melting end temperature on the DSC curve is drawn. Next, the horizontal axis of the graph passes through the point III on the DSC curve corresponding to the valley between the intrinsic peak a and the high temperature peak b (the endothermic peak present on the higher temperature side than the intrinsic peak, which is on the lowest temperature side). An intersection of a straight line perpendicular to the temperature and a straight line connecting point I and point II is defined as point IV. The area of the straight line connecting point IV and point II, the straight line connecting point III and point IV, and the portion surrounded by the DSC curve connecting point III and point II (shaded area) is the endothermic energy of the high temperature peak. It corresponds to. The high temperature peak b was obtained by obtaining the first DSC curve as described above and then lowering the temperature to room temperature at 10 ° C./min and again increasing the temperature to 200 ° C. at 10 ° C./min. Although it does not appear in the first DSC curve, the intrinsic peak appears in both the first DSC curve and the second DSC curve.
The temperature on the horizontal axis of the graph indicated by the peak of the intrinsic peak of the second DSC curve is defined as the melting point.
[0037]
In addition, the MFI of the expanded particles and the expanded particle molded body was prepared by defoaming the expanded particles and the expanded particle molded body by a heat press at 190 ° C. so that the shearing force does not act as much as possible. A small sample for measurement is cut out from the resin plate with a cutter blade or the like. It calculates | requires in JISK7210 (1995) Table 1: Condition 14 from the obtained sample.
[0038]
Moreover, the Z average molecular weight (polystyrene conversion) of an expanded particle and an expanded particle molding is calculated | required on the following conditions.
Average molecular weight measurement conditions
Measuring device: 150C manufactured by WATERS
Column: TSK-GELGMH6-HT (manufactured by Tosoh Corporation)
Measurement sample: 0.4ml
Solvent: Orthodichlorobenzene (ODCB)
Measurement temperature: 135 ° C
Fluid phase: ODCB
Flow rate: 1 ml / min.
Sample concentration: 0.2%
[0039]
【Example】
Next, the present invention will be described in detail with specific examples.
Examples 1-9, Comparative Examples 12
First, the propylene-based copolymer shown in Table 1 was melted in an extruder, and then extruded into a strand form from the extruder, and the strand was cooled and cut to produce resin particles having a weight of about 1.8 mg.
[0040]
[Table 1]
Next, in a 400 liter autoclave, 100 kg of the above resin particles, 230 liters of water, 400 g of a dispersant (kaolin), 30 g of a 20 wt% sodium dodecylbenzenesulfonate aqueous solution (Neogen S-20), and carbon dioxide as a foaming agent were charged. After holding at the one-stage holding temperature shown in Table 2, and then holding at the two-stage holding temperature, the autoclave contents were released under atmospheric pressure while holding the inside of the autoclave at the two-stage holding temperature. Carbon dioxide is supplied so that the pressure in the autoclave at the time of release becomes the pressure shown in Table 2, and continuously supplied into the autoclave so that the same pressure is maintained while the contents of the autoclave are released. did. Table 2 shows the apparent density and endothermic energy of the high-temperature peak of the obtained expanded particles (single-stage expanded particles). Next, the first-stage expanded particles were pressurized with air, applied with the internal pressure shown in Table 3, and then heated with steam at the pressure shown in the same table to expand again to obtain two-stage expanded particles. Table 3 shows the properties of the obtained two-stage expanded particles.
[0042]
[Table 2]
[Table 3]
After the expanded particles (two-stage expanded particles) obtained as described above were cured at 23 ° C. and atmospheric pressure for 24 hours, Examples 1 to 7 and Comparative Examples 1 to2Then, pressurize the foamed particles with air to 1.0 kg / cm3After applying the intraparticle pressure of G, in Examples 8 and 9, the foamed particles were not subjected to pressure treatment (the intraparticle pressure was 0 kg / cm3G), filled in a flat plate mold (250 mm × 200 mm × 50 mm), and heated and molded with steam at a pressure shown in Table 4. Table 4 shows the time required for filling the foamed particles into the mold after the mold was clamped, then heating with steam, and cooling to take out the molded body from the mold as a molding cycle.
[0045]
The obtained molded body was cured at 60 ° C. for 8 hours under atmospheric pressure, and then various physical properties of the molded body were measured. The results are shown in Table 4. The melting point, MFI, Z average molecular weight, and endothermic energy of the high temperature peak of the expanded foam molded body were the same as the values shown in Table 3 for the two-stage expanded particles.
[0046]
[Table 4]
* 1 For surface smoothness, observe the surface of the molded product.
○ ··· Smooth surface with few irregularities and wrinkles.
× ··· Inferior in surface smoothness, with many irregularities and wrinkles.
As evaluated.
[0048]
* 2 Shrinkage recovery is measured by measuring the length on the center line of each length and width of the molded product after curing, and determining the shrinkage rate relative to the mold dimensions.
○: Vertical and horizontal shrinkage ratios are 5% or less.
× ··· At least the shrinkage rate in either the vertical or horizontal direction exceeds 5%.
As evaluated.
[0049]
* 3 The fusing property is determined by observing the fracture surface of a test piece obtained by cutting a molded body into a length of 150 mm, a width of 50 mm, and a thickness of 10 mm, and pulling it at a speed of 500 mm / min with a tensile tester.
○ ... 60% or more of the fracture surface is destroyed.
×: Less than 60% of the fractured surface is destroyed.
As evaluated.
[0050]
* 4 Tensile strength and tensile elongation were measured according to JIS K6767.
[0051]
【The invention's effect】
As described above, the polypropylene resin expanded particles of the present invention use a specific propylene random copolymer or propylene random block while using a low MFI base resin, which has been conventionally considered to have low expandability. By using the copolymer as a base resin and setting the melting point, MFI, Z average molecular weight and endothermic energy of the high temperature peak in the DSC curve obtained by differential scanning calorimetry of the expanded particles to be expanded particles having a specific value, It is possible to obtain a foamed molded article having excellent secondary foaming properties and excellent fusibility between foamed particles. Further, the expanded particles of the present invention enable good molding without adjusting the pressure in the expanded particles to a high level, thereby making it possible to form a mold compared to the one in which the pressure in the expanded particles is adjusted high. Since the cooling time after filling and thermoforming is short, the molding cycle can be shortened, and the curing time for recovery of shrinkage of the obtained foamed molding can be shortened. The production efficiency can be significantly improved.
[0052]
The apparent density is 0.015-0.05 g / cmThreeIn the case of expanded particles having a high temperature peak endothermic energy of 5 to 12 J / g, an excellent expanded particle molded body can be obtained even by pressureless molding, and the pressure treatment step for the expanded particles before molding can be omitted. At the same time, this pressureless molding has a specific effect that the cooling time after molding and the curing time of the molded body can be further shortened, and the production efficiency of the molded body can be further improved.
[0053]
Furthermore, the molded body obtained from the expanded particles of the present invention has the advantages of excellent fusion between the expanded particles and excellent crack resistance.
[Brief description of the drawings]
FIG. 1 shows an example of a DSC curve of expanded particles, and is an explanatory diagram of a method for measuring endothermic energy at a high temperature peak.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34100298A JP4157206B2 (en) | 1998-10-29 | 1998-11-13 | Polypropylene resin foamed particles and molded polypropylene resin foam particles |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10-324571 | 1998-10-29 | ||
| JP10324571A JP2000129028A (en) | 1998-10-29 | 1998-10-29 | Polypropylene resin foamed particle and molded product thereof |
| JP34100298A JP4157206B2 (en) | 1998-10-29 | 1998-11-13 | Polypropylene resin foamed particles and molded polypropylene resin foam particles |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000198872A JP2000198872A (en) | 2000-07-18 |
| JP4157206B2 true JP4157206B2 (en) | 2008-10-01 |
Family
ID=26571528
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP34100298A Expired - Fee Related JP4157206B2 (en) | 1998-10-29 | 1998-11-13 | Polypropylene resin foamed particles and molded polypropylene resin foam particles |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4157206B2 (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5384028B2 (en) * | 2007-05-15 | 2014-01-08 | 株式会社カネカ | Method for producing polypropylene resin pre-expanded particles |
| US9023904B2 (en) | 2007-06-22 | 2015-05-05 | Jsp Corporation | Polypropylene resin foam particle and molding thereof |
| JP5154194B2 (en) * | 2007-10-29 | 2013-02-27 | 株式会社カネカ | Polypropylene resin foam particles |
| JP5315759B2 (en) * | 2008-04-14 | 2013-10-16 | 株式会社カネカ | Method for producing foamed molded product in polypropylene resin mold |
| JP2009256410A (en) * | 2008-04-14 | 2009-11-05 | Kaneka Corp | Method for producing polypropylene-based resin foam particle |
| JP5351433B2 (en) * | 2008-04-16 | 2013-11-27 | 株式会社カネカ | Polypropylene resin pre-expanded particles and a polypropylene resin in-mold foam molded product obtained from the polypropylene resin pre-expanded particles |
| JP5248939B2 (en) * | 2008-07-07 | 2013-07-31 | 株式会社カネカ | Polypropylene resin foam particles |
| JP5347368B2 (en) * | 2008-08-12 | 2013-11-20 | 株式会社カネカ | Polypropylene resin foam particles and in-mold foam moldings |
| JP5566634B2 (en) * | 2008-09-30 | 2014-08-06 | 株式会社カネカ | Polyolefin resin multistage expanded particles with excellent mold filling |
| JP2010173146A (en) * | 2009-01-28 | 2010-08-12 | Kaneka Corp | Method for manufacturing polypropylene-based resin in-mold foam molded body |
| EP2684910B1 (en) | 2011-03-08 | 2016-02-24 | Kaneka Corporation | Polyethylene resin foamed particles, polyethylene resin in-mold foam molded article, and method for producing polyethylene resin foamed particles |
| JP6286363B2 (en) * | 2012-11-27 | 2018-02-28 | 株式会社カネカ | POLYPROPYLENE RESIN FOAM PARTICLE, POLYPROPYLENE RESIN IN-MOLD FOAM MOLDING AND METHOD FOR PRODUCING THEM |
| JP6093604B2 (en) * | 2013-03-08 | 2017-03-08 | 株式会社ジェイエスピー | Polypropylene resin expanded particles and molded articles thereof |
| WO2023190441A1 (en) * | 2022-03-29 | 2023-10-05 | 株式会社カネカ | Polypropylene resin foam particles, polypropylene resin foam molded body, and method for manufacturing polypropylene resin foam particles |
-
1998
- 1998-11-13 JP JP34100298A patent/JP4157206B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000198872A (en) | 2000-07-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4157206B2 (en) | Polypropylene resin foamed particles and molded polypropylene resin foam particles | |
| JP5689819B2 (en) | Polyethylene resin expanded particles and polyethylene resin in-mold expanded molding | |
| JP5375613B2 (en) | Polypropylene resin pre-expanded particles and method for producing the same | |
| JP6547628B2 (en) | Polyethylene-based resin foam particles, polyethylene-based resin in-mold foam molded article and method for producing the same | |
| JPH0739501B2 (en) | Non-crosslinked linear low density polyethylene pre-expanded particles | |
| WO2018088390A1 (en) | Foam particles, and moulded article thereof | |
| EP1870434B1 (en) | Blends of ethylenic polymers with improved modulus and melt strength and articles fabricated from these blends | |
| JP2022127578A (en) | Foamed particle and method for producing the same | |
| JP3418081B2 (en) | Expanded resin particles | |
| JP3692760B2 (en) | Method for producing foamed molded product in polypropylene resin mold | |
| JP6637903B2 (en) | Polypropylene resin foam particles | |
| JP6961607B2 (en) | Foamed particle molded product | |
| US6166096A (en) | Pre-expanded particles of polypropylene resin, process for producing the same and process for producing in-mold foamed articles therefrom | |
| JP2000129028A (en) | Polypropylene resin foamed particle and molded product thereof | |
| JP2018070735A (en) | Foamed particle and method for producing foamed particle molding | |
| JP2006297807A (en) | Polypropylene-based resin in-mold foam-molding body | |
| JPH05163381A (en) | Production of expanded polymer particle | |
| CN115427487A (en) | Polypropylene resin expanded beads and molded article of polypropylene resin expanded beads | |
| JP5295730B2 (en) | Method for producing polypropylene resin pre-expanded particles | |
| JP5758586B2 (en) | Polyethylene resin expanded particles and polyethylene resin in-mold expanded molding | |
| JP3537001B2 (en) | Expanded polypropylene resin particles and method for producing the same | |
| JP2000302911A (en) | Polypropylene-based resin expanded particle for molding | |
| JP2006255993A (en) | Manufacturing method of polypropylene resin foamed product | |
| JPH04225042A (en) | Foam based on olefin copolymer | |
| JP3195675B2 (en) | Method for producing expanded polyolefin resin particles |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20051109 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20051116 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060113 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A821 Effective date: 20060113 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20060531 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060728 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060911 |
|
| A911 | Transfer of reconsideration by examiner before appeal (zenchi) |
Free format text: JAPANESE INTERMEDIATE CODE: A911 Effective date: 20060915 |
|
| A912 | Removal of reconsideration by examiner before appeal (zenchi) |
Free format text: JAPANESE INTERMEDIATE CODE: A912 Effective date: 20061027 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A821 Effective date: 20080125 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20080603 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20080711 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110718 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110718 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120718 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130718 Year of fee payment: 5 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| LAPS | Cancellation because of no payment of annual fees |