JP4660016B2 - Method for producing lightweight molded body - Google Patents
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- JP4660016B2 JP4660016B2 JP2001159831A JP2001159831A JP4660016B2 JP 4660016 B2 JP4660016 B2 JP 4660016B2 JP 2001159831 A JP2001159831 A JP 2001159831A JP 2001159831 A JP2001159831 A JP 2001159831A JP 4660016 B2 JP4660016 B2 JP 4660016B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、外観の良好な軽量成形体を容易に製造する方法に関するものである。
【０００２】
【従来の技術】
従来から、成形品の軽量化、断熱化及び吸音化等を目的として、様々な用途において樹脂の発泡体が用いられている。しかしながら、従来の発泡成形法では、発泡倍率を大きくしたり、射出速度を小さくしたりすると、発泡ガスにより成形品の表面にシルバーマークが発生し、外観を低下させる等の問題を有していた。
この問題を解決する手段として、金型のキャビティ内に不活性ガスを注入し、内圧をかけて発泡剤による発泡を抑え、その後キャビティの容積を拡大し、発泡させるカウンタープレッシャー法が提案されている。しかしながら、この方法では、設備や金型等を工夫する必要があるため、コストが高くなるという問題があった。また、この方法では、発泡粒子径が大きくなり、このため成形品の強度が低下する等の問題もあった。
これらの問題に対する対応策として、樹脂にエラストマー等を混練することにより、溶融粘度を高める方法が提案されている。しかし、、大きな溶融粘度を有するエラストマー（ゴム）を用いた場合、樹脂への分散性が悪く、成形品の外観の低下や物性の低下をもたらすため、使用できるエラストマー（ゴム）の溶融粘度が限られていた。また、流動性の良好な樹脂は、溶融粘度が低くなり過ぎてゴムの分散性を悪化させるため、用いる樹脂も限定されるという問題があった。
【０００３】
【発明が解決しようとする課題】
本発明は上記事情に鑑みなされたもので、シルバーの発生がなく、外観の良好な軽量成形体を提供することを目的とするものである。
【０００４】
【課題を解決するための手段】
本発明者らは、上記課題を解決するために鋭意研究を重ねた結果、溶融粘度の高いエラストマー（ゴム）に発泡剤を分散させたマスターバッチを用いることにより、カウンタープレッシャー法等の特殊な成形法を用いることなく、シルバーの発生がなく、外観の良好な軽量成形体を得ることができ、発泡粒子径も粗大化することなく、適度に均一化されていることを見出した。発泡粒子径が粗大化せず、適度に均一化されているのは、溶融粘度の高いゴムが発泡体中に微分散しているため、全体の溶融粘度も高くなり、発泡体の外にガスが漏れにくくなったためと考えられる。また、溶融粘度の高いゴムが微分散する理由は、ゴム中に発泡剤が微分散しており、混練時に発生するガスによりゴムの分散が助長されるためであると推定される。本発明はかかる知見に基づいて完成したものである。
すなわち、本発明は、（Ａ）温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が１０1 〜１０5 Ｐａ・ｓである熱可塑性ゴム５０〜９５質量％と、発泡剤５０〜５質量％とを混練してなる発泡剤マスターバッチ及び（Ｂ）上記熱可塑性ゴムよりも溶融粘度の低い熱可塑性樹脂をブレンドした後、該熱可塑性樹脂の溶融温度以上の温度に加熱し、発泡剤により発泡させると共に、賦形することを特徴とする軽量成形体の製造方法を提供するものである。
【０００５】
【発明の実施の形態】
本発明で用いる発泡剤マスターバッチに配合する熱可塑性ゴムは、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が１０1 〜１０5 Ｐａ・ｓのものである。この溶融粘度が１０1 Ｐａ・ｓ未満であると、軽量成形体（発泡成形体）にシルバーが発生するのを防止することができず、また、発泡セル径が大きく、かつ不揃いとなる。一方、この溶融粘度が１０5 Ｐａ・ｓを超えると、（Ｂ）成分の熱可塑性樹脂への、発泡剤マスターバッチの分散が不良となり、発泡成形体の外観や物性が低下してしまう。この溶融粘度は、ワイゼンベルグレオゴニオメーターのような円錐円盤レオメーターを用いて測定することができる。
【０００６】
熱可塑性ゴムとしては、公知のスチレン系熱可塑性エラストマー、オレフィン系熱可塑性エラストマー、ポリエステル系熱可塑性エラストマー、アミド系熱可塑性エラストマー等が挙げられる。
スチレン系熱可塑性ゴムとしては、スチレン−ブタジエンブロック共重合体（ＳＢＲ）、水素添加スチレン−ブタジエンブロック共重合体（ＳＥＢ，ＳＥＢＣ）、スチレン−ブタジエン−スチレンブロック共重合体（ＳＢＳ）、水素添加スチレン−ブタジエン−スチレンブロック共重合体（ＳＥＢＳ）、スチレン−イソプレンブロック共重合体（ＳＩＲ）、水素添加スチレン−イソプレンブロック共重合体（ＳＥＰ）、スチレン−イソプレン−スチレンブロック共重合体（ＳＩＳ）、水素添加スチレン−イソプレン−スチレンブロック共重合体（ＳＥＰＳ）、ブタジエン−アクリロニトリル−スチレン−コアシェルゴム（ＡＢＳ）、メチルメタクリレート−ブタジエン−スチレン−コアシェルゴム（ＭＢＳ）、メチルメタクリレート−ブチルアクリレート−スチレン−コアシェルゴム（ＭＡＳ）、オクチルアクリレート−ブタジエン−スチレン−コアシェルゴム（ＭＡＢＳ）、アルキルアクリレート−ブタジエン−アクリロニトリル−スチレン−コアシェルゴム（ＡＡＢＳ）、ブタジエン−スチレン−コアシェルゴム（ＳＢＲ）、メチルメタクリレート−ブチルアクリレート−シロキサンをはじめとするシロキサン含有コアシェルゴム等のコアシェルタイプの粒子状弾性体、またはこれらを変性したゴム等が挙げられる。
オレフィン系熱可塑性エラストマーとしては、エチレン−プロピレンゴム（ＥＰＲ）、エチレン−ブテン共重合体（ＥＢＲ）、エチレンプロピレンジエンゴム（ＥＰＤＭ）、硬質相がポリプロピレン又はポリエチレンで軟質相がＥＰＭ、ＥＰＤＭ等である、住友ＴＰＥ、ミラストマー（三井化学社製）、サーモラン（ＪＳＲ社製）等が挙げられる。ポリエステル系熱可塑性エラストマーとしては、硬質相がポリエステルで軟質相がポリエーテル又はポリエステルである、ハイテル（デュポン社製）、ベルプレン（東洋紡績社製）等が挙げられる。アミド系熱可塑性エラストマーとしては、硬質相がポリアミドで軟質相がポリエーテル又はポリエステルである、Ｖｅｓｔａｍｉｄ（ヒュルス社製）、クリラックスＡ（エムス社製）等が挙げられる。
このうち特に、エチレン−ブテン共重合体、ＳＥＢＳが好ましく用いられる。これらの熱可塑性ゴムは、一種を単独で又は二種以上組み合わせて用いることができる。
【０００７】
発泡剤としては、アゾジカルボン酸アミド、重炭酸ソーダとクエン酸の混合物、オキシビスベンゼンスルフォニルヒドラジド、ベンゼンスルフォニルヒドラジド、Ｐ−トルエンスルフォニルヒドラジド、ジアゾアミノベンゼン、アゾビスイソブチロニトリル等の熱分解型化学発泡剤から選ばれる一種又は二種以上を使用することができる。
（Ａ）成分の発泡剤マスターバッチにおいて、発泡剤の配合量は、熱可塑性ゴムと発泡剤との合計量中５〜５０質量％であるが、１０〜３０質量％が好ましい。
【０００８】
（Ｂ）成分の熱可塑性樹脂は、（Ａ）成分における熱可塑性ゴムよりも溶融粘度の低いものである。この熱可塑性樹脂の溶融粘度が（Ａ）成分における熱可塑性ゴムの溶融粘度よりも高いと、樹脂流動時に、粘度の低い発泡剤を含む熱可塑性ゴムが表面部に露出し、発泡性ガスによる外観（シルバー）不良が発生する。
熱可塑性樹脂としては、ポリプロピレン，ポリエチレン等のポリオレフィン系樹脂、ポリスチレン樹脂、ポリカーボネート樹脂、ポリアセタール樹脂、ポリエステル樹脂、ポリアミド等が挙げられる。これらは一種を単独で又は二種以上を組み合わせて用いることができる。
（Ａ）成分と（Ｂ）成分との使用割合は、通常（Ａ）成分１〜９９質量％に対して（Ｂ）成分９９〜１質量％であるが、好ましくは（Ａ）成分２〜６０質量％に対して（Ｂ）成分９８〜４０質量％である。
【０００９】
本発明においては、本発明の目的を損なわない範囲で、（Ａ）成分及び（Ｂ）成分に加えて、無機充填剤、酸化防止剤、核剤、可塑剤、離型剤、難燃剤、難燃助剤、顔料、染料、カーボンブラック及び帯電防止剤等の添加剤を配合することができ、これらのそれぞれについてはその一種のみを単独で、または、二種以上を組み合わせて用いることができる。
本発明軽量成形体は、射出成形法、押出成形法、ブロー成形法などの成形法により製造することができる。射出成形法としては、ショートショットの発泡射出成形法、フルショットした後のコアバックにより発泡させる射出成形法がある。本発明の軽量成形体は、発泡倍率が1.２〜５倍程度のものであるが、後者の射出成形法の場合、発泡倍率を２〜５倍とすることが容易にでき、また成形体におけるシルバーの発生も少ないものである。後者の射出成形法において、発泡は、（Ａ）成分と（Ｂ）成分のブレンド物を加熱溶融してなる溶融樹脂を、金型のキャビティーに充填した後、該キャビティーの容積が拡大する方向に金型を移動させて行なわれる。
この射出成形法において、キャビティの容積が同じであれば、射出速度が速い程シルバーは発生しにくい。本発明においては、大型成形品のようにキャビティが大きく、発泡剤を含む樹脂がキャビティ内に充満する時間がかかり、公知の発泡成形においてはシルバーが発生し易い場合でも、シルバーの発生を防止することができる。
【００１０】
【実施例】
次に、本発明を実施例によりさらに詳細に説明するが、本発明はこれらの例によってなんら限定されるものではない。
実施例１
温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が１０００Ｐａ・ｓのゴム（エチレン−ブテン共重合体）９０重量部と、発泡剤（アゾジカルボン酸アミド）１０重量部を、二軸混練機にて１００℃で混練し、発泡剤マスターバッチを得た。このマスターバッチ２０重量部と、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が2.１×１０2 Ｐａ・ｓであり、ＭＩ（メルトインデックス）が６０ｇ／１０分のポリプロピレン８０重量部とをドライブレンドし、このブレンド物を金型に充填し、樹脂温度を２００℃として射出成形により発泡成形体を得た。なお、ＭＩは、ＪＩＳ Ｋ ７２１０に準拠して、温度２３０℃、荷重２1.１８Ｎで測定した値であり、以下においても同様である。
金型のサイズは、４２０ｍｍ×１００ｍｍであり、金型のキャビティの深さは、上記ブレンド物を充填する前は２ｍｍとし、ブレンド物を充填した後、キャビティの深さが４ｍｍとなるように金型を後退させた。また、射出成形は、ブレンド物の射出速度が１０５ｍｍ／ｓｅｃ、２１０ｍｍ／ｓｅｃ、４２０ｍｍ／ｓｅｃの３条件で行なった。発泡成形体の外観を目視で判定した。また、射出速度２１０ｍｍ／ｓｅｃで得られた発泡成形体の内部を切り出し、発泡粒子の状態を電子顕微鏡にて観察した。これらの結果を表１に示す。
【００１１】
比較例１
実施例１において、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が１０００Ｐａ・ｓのゴム（エチレン−ブテン共重合体）の代わりに、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が２Ｐａ・ｓのＬＤＰＥ（低密度ポリエチレン）を用いた以外は、実施例１と同様にして発泡成形体を製造し、同様の評価を行なった。結果を表１に示す。
比較例２
実施例１で用いたＭＩが６０ｇ／１０分のポリプロピレン８２重量部と、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が８Ｐａ・ｓのゴム（エチレン−プロピレン共重合体）１８重量部を二軸混練機にて溶融混練した。この混練物８０重量部と、比較例１で得られた発泡剤マスターバッチ２０重量部とをドライブレンドし、実施例１と同様にして発泡成形体を製造し、同様の評価を行なった。結果を表１に示す。
比較例２では、射出速度が４２０ｍｍ／ｓｅｃの場合はシルバーが発現しにくくなっているが、これは、発泡性ガスが樹脂表面に拡散する速度よりも充填が速いために、発泡性ガスが樹脂内部に取り込まれることによる。
【００１２】
【表１】
実施例２
温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が１００００Ｐａ・ｓのゴム（ＳＥＢＳ）８０重量部と、発泡剤（重炭酸ソーダとクエン酸の混合物）２０重量部を、二軸混練機にて１００℃で混練し、発泡剤マスターバッチを得た。このマスターバッチ１５重量部と、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が3.６×１０2 Ｐａ・ｓであり、ＭＩ（メルトインデックス）が３０ｇ／１０分のポリプロピレン８５重量部とをドライブレンドし、このブレンド物を金型に充填し、樹脂温度を２００℃として射出成形により成形体を得た。金型のサイズは、４２０ｍｍ×１００ｍｍであり、金型のキャビティの深さは、上記ブレンド物を充填する前は２ｍｍとし、ブレンド物を充填した後、キャビティの深さが４ｍｍとなるように金型を後退させた。また、射出成形は、ブレンド物の射出速度を４２０ｍｍ／ｓｅｃとして行なった。実施例１と同様に発泡成形体の外観を目視で判定した。発泡成形体は2.５倍に膨張しており、成形体表面のシルバー等の発生もなく良好な外観であった。
【００１４】
比較例３
実施例２で用いたＭＩが３０ｇ／１０分のポリプロピレン８５重量部と、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が１００００Ｐａ・ｓのゴム（ＳＥＢＳ）１８重量部を二軸混練機にて溶融混練し、混練物を得た。次に、温度１９０℃及び剪断速度１００ｓ-1における溶融粘度が５Ｐａ・ｓのＥＶＡ（エチレン−酢酸ビニル共重合体）８０重量部と、発泡剤（重炭酸ソーダとクエン酸の混合物）２０重量部を、二軸混練機にて１００℃で混練し、発泡剤マスターバッチを得た。この発泡剤マスターバッチ１５重量部と、上記混練物８５重量部とをドライブレンドし、実施例２と同様に射出成形して発泡成形体を得た。
得られた発泡成形体は、ゴムが微分散しておらず、目視で確認できるゲルが存在すると共に、シルバーが著しく、発泡成形体の外観は劣悪であった。
【００１５】
【発明の効果】
本発明によれば、外観の良好な軽量成形体を容易に製造することができる。発泡分解ガスによるシルバーを抑制するためには、一般的に射出速度を速くするとよいといわれている。
本発明は、市販の発泡剤マスターバッチよりも、この射出速度と外観に対する条件幅を広く設定することでできるという点に特徴を有するものであり、外観に対して生産安定性を向上させるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for easily producing a lightweight molded article having a good appearance.
[0002]
[Prior art]
Conventionally, resin foams have been used in various applications for the purpose of reducing the weight, heat insulation, and sound absorption of molded products. However, in the conventional foam molding method, when the expansion ratio is increased or the injection speed is decreased, there is a problem that a silver mark is generated on the surface of the molded product due to the foaming gas and the appearance is deteriorated. .
As a means to solve this problem, a counter pressure method has been proposed in which an inert gas is injected into a mold cavity, internal pressure is applied to suppress foaming by the foaming agent, and then the volume of the cavity is expanded and foamed. . However, in this method, there is a problem that the cost is increased because it is necessary to devise facilities and molds. In addition, this method has a problem that the expanded particle diameter is increased, and thus the strength of the molded product is lowered.
As a countermeasure against these problems, a method of increasing the melt viscosity by kneading an elastomer or the like with a resin has been proposed. However, when an elastomer (rubber) having a large melt viscosity is used, the dispersibility in the resin is poor and the appearance and physical properties of the molded product are deteriorated. Therefore, the melt viscosity of the usable elastomer (rubber) is limited. It was done. Further, the resin having good fluidity has a problem that the resin used is limited because the melt viscosity becomes too low and the dispersibility of the rubber is deteriorated.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lightweight molded article having no appearance and no appearance of silver.
[0004]
[Means for Solving the Problems]
As a result of intensive research to solve the above problems, the present inventors have used special master molding such as a counter pressure method by using a master batch in which a foaming agent is dispersed in an elastomer (rubber) having a high melt viscosity. The present inventors have found that a light-weight molded article having no appearance and no appearance can be obtained without using a method, and that the foamed particle diameter is not coarsened and is appropriately uniformized. The foamed particle diameter is not coarsened and is reasonably uniform because the high melt viscosity of the rubber is finely dispersed in the foam. This is thought to be because it became difficult to leak. Further, it is estimated that the reason why the rubber having a high melt viscosity is finely dispersed is that the foaming agent is finely dispersed in the rubber and the gas generated at the time of kneading facilitates the dispersion of the rubber. The present invention has been completed based on such findings.
That is, the present invention provides (A) 50 to 95% by mass of a thermoplastic rubber having a melt viscosity of 10 1 to 10 5 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1, and 50 to 5 % by mass of a foaming agent. And (B) a thermoplastic resin having a melt viscosity lower than that of the thermoplastic rubber is blended, and then heated to a temperature equal to or higher than the melting temperature of the thermoplastic resin and foamed with the foaming agent. In addition, the present invention provides a method for producing a lightweight molded article characterized by shaping.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic rubber blended in the foaming agent master batch used in the present invention has a melt viscosity of 10 1 to 10 5 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 . When this melt viscosity is less than 10 1 Pa · s, it is impossible to prevent silver from being generated in a lightweight molded product (foamed molded product), and the foamed cell diameter is large and uneven. On the other hand, when the melt viscosity exceeds 10 5 Pa · s, the foaming agent master batch is poorly dispersed in the thermoplastic resin of the component (B), and the appearance and physical properties of the foamed molded product are deteriorated. This melt viscosity can be measured using a conical disk rheometer, such as a Weisenberg Gregorometer.
[0006]
Examples of the thermoplastic rubber include known styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and amide-based thermoplastic elastomers.
Styrenic thermoplastic rubbers include styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB, SEBC), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene. -Butadiene-styrene block copolymer (SEBS), styrene-isoprene block copolymer (SIR), hydrogenated styrene-isoprene block copolymer (SEP), styrene-isoprene-styrene block copolymer (SIS), hydrogen Addition styrene-isoprene-styrene block copolymer (SEPS), butadiene-acrylonitrile-styrene-core shell rubber (ABS), methyl methacrylate-butadiene-styrene-core shell rubber (MBS), methyl methacrylate-butyl Acrylate-styrene-core shell rubber (MAS), octyl acrylate-butadiene-styrene-core shell rubber (MABS), alkyl acrylate-butadiene-acrylonitrile-styrene-core shell rubber (AABS), butadiene-styrene-core shell rubber (SBR), methyl methacrylate Examples thereof include core-shell type particulate elastic bodies such as siloxane-containing core-shell rubbers such as butyl acrylate-siloxane, or rubbers obtained by modifying these.
Examples of the olefinic thermoplastic elastomer include ethylene-propylene rubber (EPR), ethylene-butene copolymer (EBR), ethylene propylene diene rubber (EPDM), a hard phase made of polypropylene or polyethylene, and a soft phase made of EPM, EPDM, etc. , Sumitomo TPE, Miralastomer (Mitsui Chemicals), Thermorun (JSR), etc. Examples of the polyester-based thermoplastic elastomer include Hitel (manufactured by DuPont), Belprene (manufactured by Toyobo Co., Ltd.), etc., in which the hard phase is polyester and the soft phase is polyether or polyester. Examples of the amide-based thermoplastic elastomer include Vestamid (manufactured by Huls), Clais A (manufactured by EMS), etc., in which the hard phase is polyamide and the soft phase is polyether or polyester.
Of these, ethylene-butene copolymer and SEBS are particularly preferably used. These thermoplastic rubbers can be used singly or in combination of two or more.
[0007]
As the blowing agent, thermal decomposition type chemical foaming such as azodicarboxylic acid amide, a mixture of sodium bicarbonate and citric acid, oxybisbenzenesulfonyl hydrazide, benzenesulfonyl hydrazide, P-toluenesulfonyl hydrazide, diazoaminobenzene, azobisisobutyronitrile, etc. One or more selected from agents can be used.
In the foaming agent master batch of the component (A), the blending amount of the foaming agent is 5 to 50% by mass in the total amount of the thermoplastic rubber and the foaming agent, but is preferably 10 to 30% by mass.
[0008]
The thermoplastic resin (B) has a lower melt viscosity than the thermoplastic rubber in component (A). If the melt viscosity of the thermoplastic resin is higher than the melt viscosity of the thermoplastic rubber in the component (A), the thermoplastic rubber containing the foaming agent having a low viscosity is exposed to the surface portion during the resin flow, and the appearance by the foaming gas (Silver) Defects occur.
Examples of the thermoplastic resin include polyolefin resins such as polypropylene and polyethylene, polystyrene resins, polycarbonate resins, polyacetal resins, polyester resins, and polyamides. These can be used individually by 1 type or in combination of 2 or more types.
The proportion of component (A) and component (B) used is usually 99 to 1% by weight of component (B) with respect to 1 to 99% by weight of component (A), but preferably 2 to 60 of component (A). It is 98-40 mass% of (B) component with respect to mass%.
[0009]
In the present invention, an inorganic filler, an antioxidant, a nucleating agent, a plasticizer, a release agent, a flame retardant, a flame retardant, in addition to the component (A) and the component (B), as long as the object of the present invention is not impaired. Additives such as a fuel aid, a pigment, a dye, carbon black, and an antistatic agent can be blended, and each of these can be used alone or in combination of two or more.
The lightweight molded body of the present invention can be produced by a molding method such as an injection molding method, an extrusion molding method, or a blow molding method. As the injection molding method, there are a short shot foam injection molding method and an injection molding method in which foaming is performed by a core back after full shot. The lightweight molded article of the present invention has a foaming ratio of about 1.2 to 5 times, but in the case of the latter injection molding method, the foaming ratio can be easily increased to 2 to 5 times. There is little generation of silver. In the latter injection molding method, foaming is performed by filling a cavity of a mold with a molten resin obtained by heating and melting a blend of the component (A) and the component (B), and then increasing the volume of the cavity. This is done by moving the mold in the direction.
In this injection molding method, if the cavity volume is the same, the higher the injection speed, the less likely silver will be generated. In the present invention, the cavity is large like a large molded product, and it takes time to fill the cavity with a resin containing a foaming agent, and even when silver is easily generated in known foam molding, the generation of silver is prevented. be able to.
[0010]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1
In a biaxial kneader, 90 parts by weight of a rubber (ethylene-butene copolymer) having a melt viscosity of 1000 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 and 10 parts by weight of a foaming agent (azodicarboxylic amide) are used. The mixture was kneaded at 100 ° C. to obtain a foaming agent master batch. 20 parts by weight of this master batch and 80 parts by weight of polypropylene having a melt viscosity of 2.1 × 10 2 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 and an MI (melt index) of 60 g / 10 min. Dry blending was performed, and this blend was filled into a mold, and a foamed molded article was obtained by injection molding at a resin temperature of 200 ° C. MI is a value measured at a temperature of 230 ° C. and a load of 21.18 N in accordance with JIS K 7210, and the same applies to the following.
The size of the mold is 420 mm × 100 mm, and the depth of the mold cavity is 2 mm before filling the blended product, and after filling the blended product, the mold has a depth of 4 mm. The mold was retracted. In addition, the injection molding was performed under the three conditions of the blend injection speed of 105 mm / sec, 210 mm / sec, and 420 mm / sec. The appearance of the foamed molded product was visually determined. Further, the inside of the foamed molded article obtained at an injection speed of 210 mm / sec was cut out, and the state of the foamed particles was observed with an electron microscope. These results are shown in Table 1.
[0011]
Comparative Example 1
In Example 1, the temperature 190 ° C. and a melt viscosity at a shear rate 100s -1 is 1000 Pa · s Rubber - instead of (ethylene-butene copolymer), the melt viscosity at 190 ° C. and a shear rate of 100s -1 is 2 Pa · A foamed molded article was produced in the same manner as in Example 1 except that s LDPE (low density polyethylene) was used, and the same evaluation was performed. The results are shown in Table 1.
Comparative Example 2
Two parts by weight of 82 parts by weight of polypropylene used in Example 1 and 60 parts by weight of rubber (ethylene-propylene copolymer) having a melt viscosity of 8 Pa · s at 190 ° C. and a shear rate of 100 s −1 were used. It was melt-kneaded with a shaft kneader. 80 parts by weight of this kneaded product and 20 parts by weight of the foaming agent master batch obtained in Comparative Example 1 were dry blended to produce a foamed molded product in the same manner as in Example 1, and the same evaluation was performed. The results are shown in Table 1.
In Comparative Example 2, when the injection speed is 420 mm / sec, silver is difficult to develop. This is because the filling gas is faster than the speed at which the foaming gas diffuses on the resin surface. By being taken inside.
[0012]
[Table 1]
Example 2
80 parts by weight of rubber (SEBS) having a melt viscosity of 10,000 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 and 20 parts by weight of a foaming agent (a mixture of sodium bicarbonate and citric acid) at 100 ° C. in a biaxial kneader The resulting mixture was kneaded to obtain a foaming agent master batch. 15 parts by weight of this master batch and 85 parts by weight of polypropylene having a melt viscosity of 3.6 × 10 2 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 and an MI (melt index) of 30 g / 10 min. Dry blending was performed, and this blend was filled in a mold, and a molded body was obtained by injection molding at a resin temperature of 200 ° C. The mold size is 420 mm × 100 mm, and the mold cavity depth is 2 mm before filling the blended product, and after filling the blended product, the cavity depth is 4 mm. The mold was retracted. In addition, the injection molding was performed at an injection speed of the blend of 420 mm / sec. In the same manner as in Example 1, the appearance of the foamed molded product was visually determined. The foamed molded article expanded 2.5 times, and had a good appearance without the occurrence of silver or the like on the surface of the molded article.
[0014]
Comparative Example 3
In a biaxial kneader, 85 parts by weight of polypropylene used in Example 2 and 85 parts by weight of polypropylene of 30 g / 10 min and 18 parts by weight of rubber (SEBS) having a melt viscosity of 10,000 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 are used. The mixture was melt-kneaded to obtain a kneaded product. Next, 80 parts by weight of EVA (ethylene-vinyl acetate copolymer) having a melt viscosity of 5 Pa · s at a temperature of 190 ° C. and a shear rate of 100 s −1 and 20 parts by weight of a foaming agent (a mixture of sodium bicarbonate and citric acid) It knead | mixed at 100 degreeC with the biaxial kneader, and the foaming agent masterbatch was obtained. 15 parts by weight of this foaming agent masterbatch and 85 parts by weight of the kneaded product were dry blended and injection molded in the same manner as in Example 2 to obtain a foamed molded product.
In the obtained foamed molded article, rubber was not finely dispersed, a gel that could be visually confirmed was present, silver was remarkable, and the appearance of the foamed molded article was poor.
[0015]
【The invention's effect】
According to the present invention, it is possible to easily produce a lightweight molded article having a good appearance. In order to suppress silver caused by foam decomposition gas, it is generally said that the injection speed should be increased.
The present invention is characterized in that it can be set by setting a wider range of conditions for the injection speed and the appearance than a commercially available foaming agent masterbatch, and improves the production stability with respect to the appearance. is there.
Claims (6)
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9822231B2 (en) | 2013-12-24 | 2017-11-21 | Exxonmobil Chemical Patents Inc. | Compositions comprising thermoplastic vulcanizate, foamed material and articles made therefrom |
| WO2018125391A1 (en) | 2016-12-29 | 2018-07-05 | Exxonmobil Chemical Patents Inc. | Thermoplastic vulcanizates for foaming applications |
| WO2019112724A1 (en) | 2017-12-06 | 2019-06-13 | Exxonmobil Chemical Patents Inc. | Low density foamed thermoplastic vulcanizate compositions |
| US10508184B2 (en) | 2016-12-29 | 2019-12-17 | Exxonmobil Chemical Patents Inc. | Foaming agent masterbatches for foaming thermoplastic vulcanizates |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009001772A (en) * | 2007-05-23 | 2009-01-08 | Kaneka Corp | Polypropylene resin foam injection-molded article |
| JP5489561B2 (en) * | 2009-07-07 | 2014-05-14 | 株式会社フジクラ | Foamed electric wire and transmission cable having the same |
| JP2012050016A (en) | 2010-08-30 | 2012-03-08 | Olympus Imaging Corp | Imaging apparatus |
| FR3047245B1 (en) * | 2016-01-29 | 2018-02-23 | Arkema France | COPOLYMER FOAM WITH POLYAMIDE BLOCKS AND POLYETHERS BLOCKS |
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| JPH08231747A (en) * | 1995-02-23 | 1996-09-10 | Mitsui Toatsu Chem Inc | Foam sheet of polypropylene resin composition |
| JPH08258081A (en) * | 1995-03-27 | 1996-10-08 | Nishikawa Rubber Co Ltd | Mold foaming connection molding method of thermoplastic elastomer |
| JP2000006182A (en) * | 1998-06-23 | 2000-01-11 | Chisso Corp | Foam propeller fan |
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| JPH02113035A (en) * | 1988-10-24 | 1990-04-25 | Nippon Oil Co Ltd | Preparation of master batch composition |
| JPH08231747A (en) * | 1995-02-23 | 1996-09-10 | Mitsui Toatsu Chem Inc | Foam sheet of polypropylene resin composition |
| JPH08258081A (en) * | 1995-03-27 | 1996-10-08 | Nishikawa Rubber Co Ltd | Mold foaming connection molding method of thermoplastic elastomer |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US9822231B2 (en) | 2013-12-24 | 2017-11-21 | Exxonmobil Chemical Patents Inc. | Compositions comprising thermoplastic vulcanizate, foamed material and articles made therefrom |
| WO2018125391A1 (en) | 2016-12-29 | 2018-07-05 | Exxonmobil Chemical Patents Inc. | Thermoplastic vulcanizates for foaming applications |
| US10508184B2 (en) | 2016-12-29 | 2019-12-17 | Exxonmobil Chemical Patents Inc. | Foaming agent masterbatches for foaming thermoplastic vulcanizates |
| US11192992B2 (en) | 2016-12-29 | 2021-12-07 | Exxonmobil Chemical Patents Inc. | Thermoplastic vulcanizates for foaming applications |
| WO2019112724A1 (en) | 2017-12-06 | 2019-06-13 | Exxonmobil Chemical Patents Inc. | Low density foamed thermoplastic vulcanizate compositions |
| US11447624B2 (en) | 2017-12-06 | 2022-09-20 | Celanese International Corporation | Low density foamed thermoplastic vulcanizate compositions |
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| JP2002348397A (en) | 2002-12-04 |
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