JP2005008762A - Resin composition for food container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition having excellent heat resistance and oil resistance especially at a site having strain at high temperature, hardly causing a crack, having good melt characteristics and providing a food container having good processability and impact resistance. <P>SOLUTION: The resin composition for the food container is obtained by compounding a syndiotactic styrenic polymer and a styrenic resin in a specific proportion with a polyphenylene ether resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２３】
（式中、Ｒ^１ 、Ｒ^２ 、Ｒ^３ およびＲ^４ は、それぞれ独立して、水素原子、ハロゲン原子、炭化水素基、置換炭化水素基、アルコキシ基、シアノ基、フェノキシ基またはニトロ基を表し、ｎは重合度を表わす整数である）で示される重合体の総称であって、上記一般式で示される重合体の１種単独であっても、２種以上が組み合わされた共重合体であってもよい。
【００２４】
Ｒ^１ 、Ｒ^２ 、Ｒ^３ およびＲ^４ の具体例としては、塩素原子、臭素原子、ヨウ素原子、メチル、エチル、プロピル、アリル、フェニル、ベンジル、メチルベンジル、クロロメチル、ブロモメチル、シアノエチル、シアノ、メトキシ、エトキシ、フェノキシ、ニトロなどの基が挙げられる。
【００２５】
好ましいＰＰＥ系樹脂は、上記式（Ｉ）におけるＲ^１ およびＲ^２ がアルキル基、特に炭素原子数１〜４のアルキル基であり、Ｒ^３ 、Ｒ^４は、水素原子もしくは炭素原子数１〜４のアルキル基であるポリマーである。ｎは通常５０以上が好ましい。
【００２６】
ＰＰＥ系樹脂の具体例としては、ポリ（２，６−ジメチル−１，４−フェニレン）エーテル、ポリ（２，６−ジエチル−１，４−フェニレン）エーテル、ポリ（２−メチル−６−エチル−１，４−フェニレン）エーテル、ポリ（２−メチル−６−プロピル−１，４−フェニレン）エーテル、ポリ（２，６−ジプロピル−１，４−フェニレン）エーテル、ポリ（２−エチル−６−プロピル−１，４−フェニレン）エーテル、ポリ（２，６−ジメトキシ−１，４−フェニレン）エーテル、ポリ（２，６−ジクロロメチル−１，４−フェニレン）エーテル、ポリ（２，６−ジブロモメチル−１，４−フェニレン）エーテル、ポリ（２，６−ジフェニル−１，４−フェニレン）エーテル、ポリ（２，６−ジトリル−１，４−フェニレン）エーテル、ポリ（２，６−ジクロロ−１，４−フェニレン）エーテル、ポリ（２，６−ジベンジル−１，４−フェニレン）エーテル、ポリ（２，５−ジメチル−１，４−フェニレン）エーテルなどが挙げられる。中でも特に好ましいＰＰＥ系樹脂は、ポリ（２，６−ジメチル−１，４−フェニレン）エーテルである。
【００２７】
また、ＰＰＥ系の共重合体としては、上記ポリフェニレンエーテル繰返し単位中にアルキル３置換フェノール、たとえば２，３，６−トリメチルフェノールを一部含有する共重合体を挙げることができる。また、これらのＰＰＥ系樹脂に、スチレン系化合物がグラフトした共重合体であってもよい。スチレン系化合物グラフト化ＰＰＥとしては、上記ＰＰＥ系樹脂にスチレン系化合物として、たとえば、スチレン、α−メチルスチレン、ビニルトルエン、クロロスチレンなどをグラフト重合して得られる共重合体が挙げられる。
【００２８】
また、ＰＰＥ系樹脂は、極性基を有する変性剤により変性されていてもかまわない。たとえば、酸ハライド、カルボニル基、酸無水物、酸アミド、カルボン酸エステル、酸アジド、スルフォン基、ニトリル基、シアノ基、イソシアン酸エステル、アミノ基、イミド基、水酸基、エポキシ基、オキサゾリン基、チオール基などが挙げられる。
【００２９】
本発明のＰＰＥ系樹脂のクロロホルムを溶剤として２５℃で測定した固有粘度は、０．０８〜０．６０ｄｌ／ｇであることが好ましい。該固有粘度が０．０８ｄｌ／ｇ未満であると、得られる組成物の機械的強度および伸び、耐熱性などの物性が低下し、一方、０．６０ｄｌ／ｇを超えると組成物の加工性が著しく低下する傾向にあるので、いずれも好ましくない。
【００３０】
本発明において、最も好ましいＰＰＥ系樹脂は、クロロホルムを溶剤として２５℃で測定した固有粘度が、０．１２〜０．５１ｄｌ／ｇであるポリ（２，６−ジメチル−１，４−フェニレン）エーテルである。
【００３１】
本発明の成分（Ａ）であるポリフェニレンエーテル系樹脂は、食品容器用樹脂組成物１００重量部中、５〜９５重量部、好ましくは１０〜５０重量部配合する。成分（Ａ）の配合量が、食品容器用樹脂組成物１００重量部中、５重量部未満であると、難燃性が不十分であり、一方、９５重量部を超えると耐薬品性が低下するので、いずれも好ましくない。
【００３２】
シンジオタクチックスチレン系重合体（成分（Ｂ））
本発明に用いられる（Ｂ）シンジオタクチックスチレン系重合体とは、高度のシンジオタクチック構造を有するスチレン系重合体である。シンジオタクチック構造とは、炭素−炭素結合から形成される主鎖に対してフェニル基あるいは置換フェニル基が交互に反対方向に位置する立体構造を有するものであり、そのタクティシティーは同位体炭素による核磁気共鳴法（^１３Ｃ−ＮＭＲ法）により定量される。^１３Ｃ−ＮＭＲ法により測定されるタクティシティーは、連続する複数個の構成単位の存在割合、たとえば２個の場合はダイアッド、３個の場合はトリアッド、５個の場合はペンタッドによって示すことができる。本発明において、シンジオタクチックスチレン系重合体とは、通常はダイアッド率７５％以上、好ましくは８５％以上、またはラセミペンタッド率３０％以上、好ましくは５０％以上のシンジオタクティシティーを有するスチレン系重合体である。該スチレン系重合体は、ポリスチレン、ポリ（アルキルスチレン）、ポリ（ハロゲン化スチレン）、ポリ（アルコキシスチレン）、ポリ（ビニル安息香酸エステル）およびこれらの混合物、あるいはこれらを主成分とする共重合体を包含する。なお、ここでポリ（アルキルスチレン）としては、ポリ（メチルスチレン）、ポリ（エチルスチレン）、ポリ（イソプロピルスチレン）、ポリ（ターシャリーブチルスチレン）などが挙げられ、ポリ（ハロゲン化スチレン）としては、ポリ（クロロスチレン）、ポリ（ブロモスチレン）、ポリ（フルオロスチレン）などが挙げられる。また、ポリ（アルコキシスチレン）としては、ポリ（メトキシスチレン）、ポリ（エトキシスチレン）などが挙げられる。これらの中、特に好ましいスチレン系重合体として、ポリスチレン、ポリ（ｐ−メチルスチレン）、ポリ（ｍ−メチルスチレン）、ポリ（ｐ−ターシャリーブチルスチレン）、さらにはスチレンとｐ−メチルスチレンとの共重合体を挙げることができる。
【００３３】
また、シンジオタクチックスチレン系重合体は、分子量については、特に制限はないが、重量平均分子量で１０，０００以上のものが好ましく、とりわけ５０，０００以上のものが最適である。ここで重量平均分子量が１０，０００未満であると、耐薬品性が不足する傾向がある。さらに、分子量分布についてもその広狭は制約がなく、様々なものを充当することが可能である。シンジオタクチックスチレン系重合体は、融点が２００〜３１０℃であって、従来のアタクチック構造のスチレン系重合体に比べて耐熱性が優れている。
【００３４】
このようなシンジオタクチックスチレン系重合体は、たとえば不活性炭化水素溶媒中または溶媒の非存在下に、チタン化合物、および水とトリアルキルアルミニウムの縮合生成物を触媒として、スチレン系単量体（上記スチレン系重合体に対応する単量体）を重合することにより製造することができ（たとえば特開昭６２−１０４８１８号公報、特開昭６３−２６８７０９号公報）、また市販のものを使用することもできる。
【００３５】
上記シンジオタクチックスチレン系重合体は、極性基を有する変性剤により変性されていてもかまわない。極性基としては、たとえば、酸ハライド、カルボニル基、酸無水物、酸アミド、カルボン酸エステル、酸アジド、スルフォン基、ニトリル基、シアノ基、イソシアン酸エステル、アミノ基、イミド基、水酸基、エポキシ基、オキサゾリン基、チオール基などが挙げられる。特に好ましい極性基は、酸無水物とエポキシ基であり、酸無水物の中では無水マレイン酸基が好ましい。
【００３６】
本発明の成分（Ｂ）であるシンジオタクチックスチレン系重合体は、食品容器用樹脂組成物１００重量部中、１０〜９５重量部、好ましくは１０〜３０重量部配合する。成分（Ｂ）の配合量が、食品容器用樹脂組成物１００重量部中、１０重量部未満であると、耐薬品性が不十分であり、一方、９５重量部を超えると難燃性が低下するので、いずれも好ましくない。
【００３７】
スチレン系樹脂（成分（Ｃ））
本発明にて用いられる（Ｃ）スチレン系樹脂とは、スチレン系樹脂であって上記（Ｂ）シンジオタクチックスチレン系重合体以外のシンジオタクチック構造を有さないスチレン系樹脂を意味する。
【００３８】
シンジオタクチック構造を有さないスチレン系樹脂としては、通常のラジカル重合などにて製造されるスチレン化合物の単独重合体、あるいはスチレン化合物と共重合可能な単量体を含有したものが挙げられる。上記スチレン化合物の例としては、スチレン、α−メチルスチレン、α−エチルスチレン、α−メチル−ｐ−メチルスチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレンなどのアルキル置換スチレン、ｏ−クロルスチレン、ｍ−クロルスチレン、ｐ−クロルスチレン、ｐ−ブロモスチレン、ジクロルスチレン、ジブロモスチレン、トリクロルスチレン、トリブロモスチレンなどのハロゲン化スチレンなどが挙げられるが、これらの中ではスチレン、α−メチルスチレンが好ましい。
【００３９】
また、スチレン化合物と共重合可能な単量体の例としては、たとえばアクリロニトリル、メタクリロニトリル、フマロニトリル、マレオニトリルなどのシアン化ビニルや、メタクリル酸メチル、アクリル酸メチル、メタクリル酸、アクリル酸、無水マレイン酸などが挙げられるが、これらの中では、アクリロニトリルが好ましい。
【００４０】
本発明において、特に好ましく使用される（Ｃ）スチレン系重合体は、ハイインパクトポリスチレン（以下、ＨＩＰＳと略すことがある）である。
【００４１】
ＨＩＰＳは、スチレンもしくはその誘導体、たとえばｐ−メチルスチレン、α−メチルスチレン、α−メチル−ｐ−メチルスチレン、クロロスチレン、ブロモスチレンなどの単独重合体および共重合体７０〜９９重量％と、ジエンゴム１〜３０重量％とからなるゴム変性ポリスチレンである。ＨＩＰＳを構成するジエンゴムとしては、ブタジエン、イソプレン、クロロプレンなどの共役ジエン系化合物の単独重合体、共役ジエン系化合物と不飽和ニトリル化合物または芳香族ビニル化合物との共重合体、さらには天然ゴムなどが挙げられ、１種または２種以上用いることができる。特に、ポリブタジエン、ブタジエン−スチレン共重合体が好ましい。ＨＩＰＳは、乳化重合、懸濁重合、塊状重合、溶液重合またはそれらの組み合わせの方法により得られる。
【００４２】
本発明の成分（Ｃ）であるスチレン系樹脂は、食品容器用樹脂組成物１００重量部中、０〜８５重量部、好ましくは４０〜６０重量部配合する。成分（Ｃ）の配合量が、食品容器用樹脂組成物１００重量部中、８５重量部を超えると耐薬品性が不十分となり、かつ難燃性が低下するので、好ましくない
熱可塑性エラストマー（成分（Ｄ））
本発明の食品容器用樹脂組成物に使用する（Ｄ）熱可塑性エラストマーとしては、スチレン系熱可塑性エラストマー、ポリ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などが挙げられるが、特にスチレン系熱可塑性エラストマーであるスチレンとブタジエンまたはスチレンとイソプレンとのブロック共重合体、またはその水素添加物を用いることが好ましい。
【００４３】
以下に、スチレン系ブロック共重合体の水素添加物について詳述する。
【００４４】
本発明の成分（Ｄ）として好ましく用いられる水添スチレン系ブロック共重合体は、少なくとも２個のビニル芳香族化合物を主体とする重合体ブロックＡと、少なくとも１個の共役ジエン化合物を主体とする重合体ブロックＢとからなるブロック共重合体を水素添加して得られるものであり、たとえばＡ−Ｂ−Ａ、Ｂ−Ａ−Ｂ−Ａ、（Ａ−Ｂ）_４−Ｓｉ、Ａ−Ｂ−Ａ−Ｂ−Ａなどの構造を有するビニル芳香族化合物−共役ジエン化合物ブロック共重合体の水素添加物である。
【００４５】
この水添ブロック共重合体は、ビニル芳香族化合物を５〜６０重量％、好ましくは１０〜５０重量％含有し、さらにブロック構造については、ビニル芳香族化合物を主体とする重合体ブロックＡが、ビニル芳香族化合物重合体ブロック、またはビニル芳香族化合物が５０重量％を超え、好ましくは７０重量％以上含有するビニル芳香族化合物と、水素添加された共役ジエン化合物との共重合体ブロック構造を有しており、そしてさらに、水素添加された共役ジエン化合物を主体とする重合体ブロックＢが、水素添加された共役ジエン化合物重合体ブロック、または水素添加された共役ジエン化合物が５０重量％を超え、好ましくは７０重量％以上含有する水素添加された共役ジエン化合物と、ビニル芳香族化合物との共重合体ブロック構造を有するものである。
【００４６】
また、これらのビニル芳香族化合物を主体とする重合体ブロックＡ、水素添加された共役ジエン化合物を主体とする重合体ブロックＢは、それぞれの重合体ブロックにおける分子鎖中のビニル芳香族化合物または水素添加された共役ジエン化合物の分布がランダム、テーパード（分子鎖に沿ってモノマー成分が増加または減少するもの）、一部ブロック状またはこれらの任意の組み合わせでなっていてもよく、さらに該ビニル芳香族化合物を主体とする重合体ブロックおよび該水素添加された共役ジエン化合物を主体とする重合体ブロックがそれぞれ２個以上ある場合には、各重合体ブロックはそれぞれが同一の構造であってもよく、異なる構造であってもよい。
【００４７】
水添ブロック共重合体を構成するビニル芳香族化合物としては、たとえばスチレン、α−メチルスチレン、ビニルトルエン、ｐ−ターシャリーブチルスチレンのうちから１種または２種以上が選択でき、中でもスチレンが好ましい。また水素添加された共役ジエン化合物を構成する水添前の共役ジエン化合物としては、たとえばブタジエン、イソプレン、１，３−ペンタジエン、２，３−ジメチル−１，３−ブタジエンなどのうちから１種または２種以上が選ばれ、中でもブタジエン、イソプレンおよびこれらの組み合わせが好ましい。そして、水添される前の共役ジエン化合物を主体とする重合体ブロックは、そのブロックにおけるミクロ構造を任意に選ぶことができ、たとえば、ポリブタジエンブロックにおいては、１，２−ミクロ構造が２０〜５０％、好ましくは２５〜４５％である。
【００４８】
また、上記の構造を有する本発明に供する水添スチレン系ブロック共重合体の数平均分子量は、５，０００〜１０００，０００、好ましくは１０，０００〜８００，０００、さらに好ましくは３０，０００〜５００，０００の範囲であり、分子量分布〔重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）との比（Ｍｗ／Ｍｎ）〕は、１０以下のものである。さらに、水添ブロック共重合体の分子構造は、直鎖状、分岐状、放射状あるいはこれら任意の組み合わせのいずれであってもよい。
【００４９】
これらのブロック共重合体の製造方法は、上記の構造を有するものであればどのような製造方法で得られるものであってもかまわない。たとえば、特公昭４０−２３７９８号公報に記載された方法により、リチウム触媒などを用いて不活性溶媒中でビニル芳香族化合物−共役ジエン化合物ブロック共重合体を合成し、次いで、かかるビニル芳香族化合物−共役ジエン化合物ブロック共重合体の水素添加物の製造方法としては、たとえば特公昭４２−８７０４号公報、特公昭４３−６６３６号公報に記載された方法で得ることもできるが、特に、得られる水添ブロック共重合体の耐候性、耐熱劣化性に優れた性能を発揮するチタン系水添触媒を用いて合成された水添ブロック共重合体が好ましく、たとえば特開昭５９−１３３２０３号公報、特開昭６０−７９００５号公報に記載された方法により、不活性溶媒中でチタン系水添触媒の存在下に水素添加して、本発明に供する水添ブロック共重合体を合成することができる。
【００５０】
その際、ビニル芳香族化合物−共役ジエン化合物ブロック共重合体の共役ジエン化合物に基づく脂肪族二重結合は、少なくとも８０％を水素添加せしめ、共役ジエン化合物を主体とする重合体ブロックを形態的にオレフィン性化合物重合体ブロックに変換させることができる。また、ビニル芳香族化合物を主体とする重合体ブロックＡ、および必要に応じて共役ジエン化合物を主体とする重合体ブロックＢに共重合されているビニル芳香族化合物に基づく芳香族二重結合の水素添加率については特に制限はないが、水素添加率を２０％以下にすることが好ましい。該水添ブロック共重合体中に含まれる未水添の脂肪族二重結合の量は、赤外分光光度計、核磁気共鳴装置などにより容易に知ることができる。
【００５１】
本発明において、成分（Ｄ）の熱可塑性エラストマーは、食品容器用樹脂組成物（成分（Ａ）＋成分（Ｂ）＋成分（Ｃ））１００重量部に対し、１〜１００重量部、好ましくは１０〜９０重量部配合する。成分（Ｄ）の配合量が、食品容器用樹脂組成物（成分（Ａ）＋成分（Ｂ）＋成分（Ｃ））１００重量部に対し、１重量部未満であると、引張りの破断伸びが不十分であり、一方、１００重量部を超えると耐薬品性や難燃性が低下するので、いずれも好ましくない。
【００５２】
添加剤
本発明の食品容器用樹脂組成物には、上記の成分（Ａ）〜成分（Ｃ）、または成分（Ａ）〜成分（Ｄ）の他に、その物性を損なわない限りにおいて食品容器用樹脂組成物の混合時または成形時に他の樹脂、慣用の添加剤、たとえば、顔料、染料、難燃助剤、補強剤（ガラス繊維、炭素繊維、ウィスカーなど）、充填剤（カーボンブラック、シリカ、酸化チタン、マイカ、タルク、炭酸カルシウム、チタン酸カリウム、ワラストナイトなど）、耐熱剤、酸化防止剤、耐候剤、紫外線吸収剤、光安定化剤、滑剤、離型剤、造核剤、可塑剤（オイル、低分子量ポリエチレン、エポキシ化大豆油、ポリエチレングリコール、脂肪酸エステル類など）、流動性改良剤、帯電防止剤、相溶化剤（無水マレイン酸、クエン酸のようなジカルボン酸およびその無水物など）、抗菌剤などを添加してもよい。
【００５３】
光安定化剤や紫外線吸収剤、たとえば、ヒンダードアミン化合物系、ベンゾエート化合物系、ベンゾトリアゾール系、ベンゾフェノン系やホルムアミジン系などは、耐候性の付与・向上に有効である。また、造核剤、たとえば、タルクなどの無機系、または芳香族カルボン酸の金属塩、ソルビトール系もしくは芳香族リン酸金属塩などの有機系の造核剤は、剛性や耐傷つき性の付与・向上に有効である。
【００５４】
食品容器用樹脂組成物および成形体の製造方法
本発明の食品容器用樹脂組成物を製造するための方法に、特に制限はなく、上記の各成分を用いて種々の方法で製造することができる。しかしながら、溶融混練法が好ましい。溶融混練時に少量の溶剤の使用も可能であるが、一般には必要ない。溶融混練装置としては、一軸押出機、二軸押出機、バンバリーミキサー、ロールミキサー、ニーダー、ブラベンダープラストグラフなどを例として挙げることができるが、二軸押出機を用いた溶融混練方法が最も好ましい。溶融混練温度は、特に限定されるものではないが、通常１５０〜３５０℃の範囲である。
【００５５】
このようにして得られた本発明の食品容器用樹脂組成物を用いて、射出成形により食品容器を成形する。
【００５６】
本発明の食品容器用樹脂組成物にて成形される成形体としては、一般の食品容器の他、たとえば、大皿、プレート、トレー、ボウル、カップ、蓋などを挙げることができる。特に、本発明の食品容器用樹脂組成物にて成形される食品容器としては、電子レンジ加熱時に、食用油が付着していたとしても、該食品容器が熱破損または熱変形しないような、たとえば、弁当箱などの透明蓋または弁当箱などの本体容器に用いられることが好ましい。また、弁当箱などの本体容器は、非発泡体であっても、発泡体であってもよい。
【００５７】
【実施例】
本発明の食品容器用樹脂組成物を、さらに詳細に説明するために、以下に実施例を示して具体的に説明するが、本発明は、その趣旨を逸脱しない限り、これによって限定されるものではない
なお、実施例においては以下の樹脂を使用した。
【００５８】
成分（Ａ）：ＰＰＥ系樹脂：固有粘度（クロロホルム、２５℃）０．４０ｄｌ／ｇのポリ（２，６−ジメチル−１，４−フェニレン）エ−テル（商標；ＰＰＯ６４０、日本ジーイープラスチックス株式会社製）、
成分（Ｂ）：シンジオタクチックスチレン系重合体（ｓ−ＰＳ）：分子量１８万、^１３Ｃ−ＮＭＲの分析によるラセミペンタッド率で表したシンジオタクティシティーが９８％のシンジオタクチックポリスチレン（商標；ザレック１３０ＺＣ、出光石油化学株式会社製）、
成分（Ｃ）：スチレン系樹脂（ＰＳ）：ハイインパクトスチレン系樹脂（ＨＩＰＳ）（商標；８７０ＳＴ，日本ポリスチレン株式会社製）。
【００５９】
【実施例１〜２および比較例１〜２】
表１に示す割合（重量部）の各成分を、３０ｍｍ二軸押出機を用いて混練温度２８０℃、回転数２８０ｒｐｍにて溶融混練して、ペレットを作成した。このペレットを用い、温度２８０℃、金型温度６０℃の条件にて射出成形し試験片を作成した。
【００６０】
また、得られたペレットを用いて、０．５ｍｍ厚さの食品容器を模した成型品を、温度２８０℃にてプレス成形した。このシートから幅１２．７ｍｍ、長さ７５ｍｍの試験片を切り出し、耐油性評価用試験片とした。
【００６１】
得られた試験片について以下の特性評価を行った。結果を表１に示す。
【００６２】
以下に、特性評価に用いた測定方法を記載する。
（１）加熱撓み温度（ＨＤＴ）：ＡＳＴＭ Ｄ６４８に従って測定を行った。
（２）引張り強度（ＴＳ）：ＡＳＴＭ Ｄ６３８に従って測定を行った。
（３）耐薬品性：上記で作成した０．５ｍｍ厚試験片を、表面に０．６％の歪がかかる状態に曲げて固定し（図１）、その表面にサラダ油を塗布して出力５００Ｗの電子レンジにて９０秒加熱した。その後の状態変化を観察した。
【００６３】
評価基準としては、上記条件にて試験片の破断が生じなかったものを○、破断を生じたものを×とした。
【００６４】
【表１】

【００６５】
【発明の効果】
本発明の食品容器用樹脂組成物から成形される成形体は、耐熱性に優れる他、特に高温下における耐油性（耐薬品性）に優れ、さらに溶融特性が良好で加工性および耐衝撃性にも優れるので、冷凍・電子レンジ対応食品容器並びに高脂肪食品用容器としてその利用価値は極めて大きい。
【図面の簡単な説明】
【図１】耐薬品性試験方法[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin composition for food containers containing a polyphenylene ether (hereinafter sometimes abbreviated as PPE) resin. More specifically, the present invention is excellent in heat resistance, particularly chemical resistance typified by oil resistance at high temperatures. It is related with the resin composition for food containers which is excellent in property.
[0002]
[Prior art]
In general, amorphous (amorphous) resin is excellent in molding dimensional accuracy at the time of injection molding due to its amorphous structural characteristics, so it is often used in industrial fields that require large molded products and assembly accuracy. Has been. However, because of its amorphous structure, it has a disadvantage that it is poor in organic chemical permeability, that is, in chemical resistance, and is easily affected by oil, organic solvent and the like.
[0003]
Crystalline resins, on the other hand, have excellent chemical resistance due to their crystallinity and are used in applications where many oils and organic solvents come into contact with them. Since the phenomenon occurs and the molding dimensional accuracy is poor, it is not suitable for large molded products. In order to improve it, attempts have been made to add inorganic fillers such as glass fibers.However, the specific gravity is increased, the ductile impact strength is reduced, or the shrinkage is different in the injection molding flow direction and the flow vertical direction. And a defect of deformation occurs.
[0004]
Polyphenylene ether resins are representative of amorphous thermoplastic resins with a high softening point, have balanced mechanical properties and excellent electrical properties, and have low water absorption and good dimensional stability. is there. Moreover, the polyphenylene ether resin is very well compatible with the polystyrene resin, which is also an amorphous thermoplastic resin, and can be easily modified. A resin composition comprising a PPE resin and a styrene resin (hereinafter sometimes abbreviated as a PPE / PS resin composition) is excellent in molding processability and impact resistance (US Pat. No. 3,383,435). No. (Patent Document 1)), it has been widely used for automobile members, electric / electronic members, and the like. However, this PPE / PS resin composition is an amorphous resin and has insufficient chemical resistance, particularly resistance to an aromatic hydrocarbon solvent, as described above. In some cases, when a part having a residual molding strain is touched, crazes or cracks are generated from the part, leading to breakage of the member. For this reason, there are actual restrictions on its applications. For example, parts such as office equipment and computer-related equipment (such as internal parts, fan motor cases, Plastic chassis); used in home appliances, commercial electrical appliance parts that may be exposed to salad oil, tempura oil, and other organic solvents; or in environments where oily smoke or organic gases can be trapped (eg, factory environment, construction) Application is avoided for applications such as parts of electrical and electronic equipment.
[0005]
This is considered to be an essential drawback due to the amorphous nature of the polyphenylene ether resin.
[0006]
Many attempts have been made in the past to improve this drawback, but no technology has been obtained to improve the chemical resistance without impairing the properties of the PPE / PS resin composition. Typical prior arts include, for example, PPE / PS resin compositions, crystalline resins such as polyolefins (eg polyethylene, polypropylene, EEA), polyesters, nylons, etc .; low molecular weight olefins (eg polybutenes, ethylene oligomers etc.) Or a rubbery polymer (for example, SEBS, SBS, SEPS rubber, etc.). However, in this technique, chemical resistance is slightly improved by addition of a small amount, but when the addition amount is increased in order to exert a practical level of chemical resistance, the excellent mechanical properties inherently possessed by the PPE / PS resin composition are obtained. Not only will the strength, heat resistance, and flame retardance be reduced, but it may cause a delamination phenomenon during injection molding due to insufficient compatibility, or a defect in dimensional accuracy during molding.
[0007]
In recent years, a crystalline styrene polymer having a syndiotactic structure in a three-dimensional structure (hereinafter sometimes referred to as a syndiotactic styrene polymer) has been developed and commercialized (Japanese Patent Laid-Open No. 62-10482). Gazette (patent document 2) etc.). As a natural result, attempts have been made to blend this syndiotactic styrene polymer with various resins.
[0008]
Since syndiotactic styrene polymers have crystallinity and have a molecular structure mainly composed of a styrene skeleton, they have good compatibility with polyphenylene ether resins as well as conventional atactic styrene polymers. A blend composition of a polyphenylene ether resin and a syndiotactic styrene polymer is also known.
[0009]
However, the above-mentioned composition is often a simple composition in which a syndiotactic styrene-based polymer and a polyphenylene ether resin are alloyed, and there are few specific examples for clarifying the chemical resistance improvement and the composition synergistic effect. . Slightly, JP-A-2-64140 (Patent Document 3), JP-A-2-92948 (Patent Document 4), JP-A-9-52958 (Patent Document 5) and JP-A-9-52959 ( Patent Document 6) only describes an improvement in chemical resistance. In these publications, the chemical resistance is simply improved by adding a syndiotactic styrene polymer and an additive-type rubber-like elastic body to the polyphenylene ether resin and increasing the crystalline component. However, since the dimensional accuracy characteristic of the polyphenylene ether resin that is amorphous is not taken into consideration, the practicality is poor.
[0010]
From these facts, the polyphenylene ether resin is completely compatible with the polyphenylene ether resin and has excellent chemical resistance such as oil resistance in a strained portion, that is, does not cause craze and cracks. A composition is desired.
[0011]
Moreover, as for the tableware used for a meal, a dining room, and the container which preserve | saves processed foods, such as a retort food, the thing made from a synthetic resin is used from a viewpoint of safety | security and weight reduction. Conventionally, melamine resin, polystyrene (PS), polypropylene (PP), polycarbonate (PC) and the like have been mainly used as materials for synthetic resin food containers. However, the melamine resin container has weak mechanical strength and is brittle, and there is a possibility that uncured material may be eluted and mixed into food. The PS container has insufficient oil resistance as described above, and PP The container made has a small surface hardness and is easily scratched. Further, since the heat resistance is insufficient, the container was easily deformed when sterilized by steam. The PC container is excellent in heat resistance and mechanical strength, but when sterilized with steam, it is whitened by hydrolysis and the appearance is easily damaged. Furthermore, there is a risk that bisphenol A, which is a suspected endocrine disrupting substance, which has recently become a problem, is eluted from PC containers.
[0012]
Therefore, the appearance of a resin composition for food containers that has excellent heat resistance against heat treatment such as steam sterilization and also has oil resistance to edible oil, salad oil, and the like, that is, chemical resistance, has been desired.
[0013]
[Patent Document 1]
US Pat. No. 3,383,435
[Patent Document 2]
Japanese Patent Laid-Open No. 62-10481
[Patent Document 3]
JP-A-2-64140
[Patent Document 4]
Japanese Patent Laid-Open No. 2-92948
[Patent Document 5]
JP-A-9-52958
[Patent Document 6]
JP 9-52959 A
[0014]
[Problems to be solved by the invention]
The present invention eliminates the above-mentioned disadvantages of the prior art, and is excellent in heat resistance against heat treatment such as steam sterilization, particularly in oil resistance (chemical resistance) at a strained portion under high temperature, and crazing and cracking. It is an object of the present invention to provide a resin composition that gives a food container that does not produce (cracks), has good melting characteristics, and is excellent in workability and impact resistance.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have made various studies, and as a result, they are obtained by blending a polyphenylene ether resin with a syndiotactic styrene polymer and a styrene resin at a specific ratio. The present invention is completed by finding that the resin composition can be a food container having excellent heat resistance and oil resistance (chemical resistance) at a strained portion at high temperature, and further excellent in workability and impact resistance. Has been reached.
[0016]
That is, according to the first invention of the present invention, (A) 5 to 90 parts by weight of a polyphenylene ether resin, (B) 10 to 95 parts by weight of a syndiotactic styrene polymer, and (C) styrene resin 0 to A resin composition for food containers containing 85 parts by weight (provided that component (A) + component (B) + component (C) = 100 parts by weight) is provided.
[0017]
Moreover, according to 2nd invention of this invention, with respect to 100 weight part of resin compositions for food containers in 1st invention, the resin composition for food containers further contains (D) 1-100 weight part of thermoplastic elastomers. Things are provided.
[0018]
Further, according to the third invention of the present invention, in the first or second invention, the polyphenylene ether resin of the component (A) has an intrinsic viscosity of 0.08 measured at 25 ° C. using chloroform as a solvent. There is provided a resin composition for food containers which is poly (2,6-dimethyl-1,4-phenylene) ether in the range of ˜0.60 dl / g.
[0019]
Further, according to a fourth invention of the present invention, in the second or third invention, the thermoplastic elastomer of the component (D) is a block copolymer of styrene and butadiene or styrene and isoprene, or hydrogen thereof. A resin composition for food containers as an additive is provided.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The resin composition for food containers of the present invention will be described in detail.
[0021]
Polyphenylene ether resin (component (A))
In this invention, a well-known thing can be used as PPE-type resin of a component (A). That is, the PPE resin is, for example, the following general formula (I):
[0022]
[Chemical 1]

[0023]
(Wherein R¹ , R² , R³ And R⁴Each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group, a substituted hydrocarbon group, an alkoxy group, a cyano group, a phenoxy group or a nitro group, and n is an integer representing the degree of polymerization). It is a general term for a combination, and may be a single polymer represented by the above general formula or a copolymer in which two or more types are combined.
[0024]
R¹ , R² , R³And R⁴ Specific examples of these include groups such as chlorine atom, bromine atom, iodine atom, methyl, ethyl, propyl, allyl, phenyl, benzyl, methylbenzyl, chloromethyl, bromomethyl, cyanoethyl, cyano, methoxy, ethoxy, phenoxy, and nitro. Can be mentioned.
[0025]
A preferred PPE resin is R in the above formula (I).¹ And R² Is an alkyl group, particularly an alkyl group having 1 to 4 carbon atoms, and R³, R⁴Is a polymer which is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n is usually preferably 50 or more.
[0026]
Specific examples of the PPE resin include poly (2,6-dimethyl-1,4-phenylene) ether, poly (2,6-diethyl-1,4-phenylene) ether, and poly (2-methyl-6-ethyl). -1,4-phenylene) ether, poly (2-methyl-6-propyl-1,4-phenylene) ether, poly (2,6-dipropyl-1,4-phenylene) ether, poly (2-ethyl-6) -Propyl-1,4-phenylene) ether, poly (2,6-dimethoxy-1,4-phenylene) ether, poly (2,6-dichloromethyl-1,4-phenylene) ether, poly (2,6- Dibromomethyl-1,4-phenylene) ether, poly (2,6-diphenyl-1,4-phenylene) ether, poly (2,6-ditolyl-1,4-phenylene) ether, poly (2,6-dichloro-1,4-phenylene) ether, poly (2,6-dibenzyl-1,4-phenylene) ether, poly (2,5-dimethyl-1,4-phenylene) ether, etc. . Among them, a particularly preferable PPE resin is poly (2,6-dimethyl-1,4-phenylene) ether.
[0027]
Examples of the PPE copolymer include a copolymer partially containing an alkyl trisubstituted phenol such as 2,3,6-trimethylphenol in the polyphenylene ether repeating unit. A copolymer obtained by grafting a styrene compound onto these PPE resins may also be used. Examples of the styrene compound grafted PPE include a copolymer obtained by graft polymerization of the above PPE resin with a styrene compound such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene and the like.
[0028]
In addition, the PPE resin may be modified with a modifier having a polar group. For example, acid halide, carbonyl group, acid anhydride, acid amide, carboxylic acid ester, acid azide, sulfone group, nitrile group, cyano group, isocyanate ester, amino group, imide group, hydroxyl group, epoxy group, oxazoline group, thiol Groups and the like.
[0029]
The intrinsic viscosity of the PPE resin of the present invention measured at 25 ° C. using chloroform as a solvent is preferably 0.08 to 0.60 dl / g. When the intrinsic viscosity is less than 0.08 dl / g, physical properties such as mechanical strength, elongation and heat resistance of the resulting composition are deteriorated. On the other hand, when it exceeds 0.60 dl / g, the workability of the composition is decreased. Since they tend to be remarkably lowered, neither is preferable.
[0030]
In the present invention, the most preferable PPE resin is poly (2,6-dimethyl-1,4-phenylene) ether having an intrinsic viscosity of 0.12 to 0.51 dl / g measured at 25 ° C. using chloroform as a solvent. It is.
[0031]
The polyphenylene ether resin which is the component (A) of the present invention is blended in an amount of 5 to 95 parts by weight, preferably 10 to 50 parts by weight, in 100 parts by weight of the resin composition for food containers. When the blending amount of the component (A) is less than 5 parts by weight in 100 parts by weight of the resin composition for food containers, the flame retardancy is insufficient. On the other hand, when it exceeds 95 parts by weight, the chemical resistance is lowered. Therefore, neither is preferable.
[0032]
Syndiotactic styrene polymer (component (B))
The (B) syndiotactic styrene polymer used in the present invention is a styrene polymer having a highly syndiotactic structure. The syndiotactic structure is a structure in which phenyl groups or substituted phenyl groups are alternately positioned in opposite directions with respect to the main chain formed from carbon-carbon bonds, and the tacticity is determined by isotope carbon. Nuclear magnetic resonance (¹³C-NMR method).¹³The tacticity measured by the C-NMR method can be represented by the abundance ratio of a plurality of consecutive structural units, for example, a dyad for two, a triad for three, a pentad for five. In the present invention, the syndiotactic styrene-based polymer is usually styrene having a syndiotacticity with a dyad ratio of 75% or more, preferably 85% or more, or a racemic pentad ratio of 30% or more, preferably 50% or more. Based polymer. The styrenic polymer is polystyrene, poly (alkyl styrene), poly (halogenated styrene), poly (alkoxy styrene), poly (vinyl benzoate), a mixture thereof, or a copolymer based on these. Is included. Here, examples of the poly (alkyl styrene) include poly (methyl styrene), poly (ethyl styrene), poly (isopropyl styrene), poly (tertiary butyl styrene), and the like. , Poly (chlorostyrene), poly (bromostyrene), poly (fluorostyrene) and the like. Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Among these, particularly preferred styrenic polymers include polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tertiarybutylstyrene), and further styrene and p-methylstyrene. Mention may be made of copolymers.
[0033]
The syndiotactic styrenic polymer is not particularly limited in terms of molecular weight, but preferably has a weight average molecular weight of 10,000 or more, and particularly preferably 50,000 or more. Here, when the weight average molecular weight is less than 10,000, chemical resistance tends to be insufficient. Furthermore, the molecular weight distribution is not limited in its breadth and width, and various types can be used. The syndiotactic styrene-based polymer has a melting point of 200 to 310 ° C. and is excellent in heat resistance as compared with a conventional tactic polymer having an atactic structure.
[0034]
Such a syndiotactic styrenic polymer is obtained by using, for example, a styrene monomer (in the presence of an inert hydrocarbon solvent or in the absence of a solvent) using a titanium compound and a condensation product of water and trialkylaluminum as a catalyst. (Monomers corresponding to the styrenic polymers) can be produced by polymerization (for example, Japanese Patent Laid-Open Nos. 62-104818 and 63-268709), or commercially available products can be used. You can also.
[0035]
The syndiotactic styrene-based polymer may be modified with a modifying agent having a polar group. Examples of polar groups include acid halides, carbonyl groups, acid anhydrides, acid amides, carboxylic acid esters, acid azides, sulfone groups, nitrile groups, cyano groups, isocyanate esters, amino groups, imide groups, hydroxyl groups, and epoxy groups. , An oxazoline group, a thiol group, and the like. Particularly preferred polar groups are acid anhydrides and epoxy groups, and among the acid anhydrides, maleic anhydride groups are preferred.
[0036]
The syndiotactic styrene polymer which is the component (B) of the present invention is blended in an amount of 10 to 95 parts by weight, preferably 10 to 30 parts by weight, in 100 parts by weight of the resin composition for food containers. If the blending amount of component (B) is less than 10 parts by weight in 100 parts by weight of the resin composition for food containers, chemical resistance is insufficient, while if it exceeds 95 parts by weight, flame retardancy is reduced. Therefore, neither is preferable.
[0037]
Styrenic resin (component (C))
The (C) styrenic resin used in the present invention means a styrenic resin that does not have a syndiotactic structure other than the (B) syndiotactic styrenic polymer.
[0038]
Examples of the styrenic resin having no syndiotactic structure include a homopolymer of a styrene compound produced by ordinary radical polymerization or the like, or a monomer containing a monomer copolymerizable with the styrene compound. Examples of the styrene compound include alkyl-substituted styrene such as styrene, α-methylstyrene, α-ethylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o -Halogenated styrene such as chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, dichlorostyrene, dibromostyrene, trichlorostyrene, tribromostyrene, etc., among these, styrene, α -Methylstyrene is preferred.
[0039]
Examples of monomers copolymerizable with styrene compounds include vinyl cyanide such as acrylonitrile, methacrylonitrile, fumaronitrile, maleonitrile, methyl methacrylate, methyl acrylate, methacrylic acid, acrylic acid, maleic anhydride. An acid etc. are mentioned, Among these, acrylonitrile is preferable.
[0040]
In the present invention, the (C) styrenic polymer that is particularly preferably used is high impact polystyrene (hereinafter sometimes abbreviated as HIPS).
[0041]
HIPS is composed of 70 to 99% by weight of homopolymers and copolymers of styrene or derivatives thereof such as p-methylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, and diene rubber. It is a rubber-modified polystyrene composed of 1 to 30% by weight. Examples of the diene rubber constituting HIPS include homopolymers of conjugated diene compounds such as butadiene, isoprene, and chloroprene, copolymers of conjugated diene compounds and unsaturated nitrile compounds or aromatic vinyl compounds, and natural rubber. 1 type or 2 types or more can be used. In particular, polybutadiene and a butadiene-styrene copolymer are preferable. HIPS can be obtained by emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, or a combination thereof.
[0042]
The styrene resin which is the component (C) of the present invention is blended in an amount of 0 to 85 parts by weight, preferably 40 to 60 parts by weight, in 100 parts by weight of the resin composition for food containers. If the amount of component (C) exceeds 85 parts by weight in 100 parts by weight of the resin composition for food containers, the chemical resistance becomes insufficient and the flame retardancy is lowered, which is not preferable.
Thermoplastic elastomer (component (D))
Examples of the thermoplastic elastomer (D) used in the resin composition for food containers of the present invention include styrene thermoplastic elastomers, polyolefin thermoplastic elastomers, polyester thermoplastic elastomers and the like, and in particular, styrene thermoplastic elastomers. It is preferable to use a block copolymer of styrene and butadiene or styrene and isoprene, or a hydrogenated product thereof.
[0043]
Hereinafter, the hydrogenated product of the styrenic block copolymer will be described in detail.
[0044]
The hydrogenated styrene block copolymer preferably used as the component (D) of the present invention is mainly composed of a polymer block A mainly composed of at least two vinyl aromatic compounds and at least one conjugated diene compound. It is obtained by hydrogenating a block copolymer comprising a polymer block B, for example, A-B-A, B-A-B-A, (A-B)₄It is a hydrogenated product of vinyl aromatic compound-conjugated diene compound block copolymer having a structure such as -Si, ABABABA.
[0045]
The hydrogenated block copolymer contains a vinyl aromatic compound in an amount of 5 to 60% by weight, preferably 10 to 50% by weight, and the block structure is a polymer block A mainly composed of a vinyl aromatic compound. It has a copolymer block structure of a vinyl aromatic compound polymer block or a vinyl aromatic compound containing more than 50% by weight of vinyl aromatic compound, preferably 70% by weight or more, and a hydrogenated conjugated diene compound. And the polymer block B mainly composed of a hydrogenated conjugated diene compound has a hydrogenated conjugated diene compound polymer block, or the hydrogenated conjugated diene compound exceeds 50% by weight, Preferably, a copolymer block structure of a hydrogenated conjugated diene compound containing 70% by weight or more and a vinyl aromatic compound is formed. It is intended to.
[0046]
Further, the polymer block A mainly composed of these vinyl aromatic compounds and the polymer block B mainly composed of a hydrogenated conjugated diene compound are composed of the vinyl aromatic compound or hydrogen in the molecular chain in each polymer block. The distribution of the added conjugated diene compound may be random, tapered (in which the monomer component increases or decreases along the molecular chain), partially in a block shape, or any combination thereof, and further the vinyl aromatic When there are two or more polymer blocks mainly composed of a compound and two or more polymer blocks mainly composed of the hydrogenated conjugated diene compound, each polymer block may have the same structure, Different structures may be used.
[0047]
As the vinyl aromatic compound constituting the hydrogenated block copolymer, for example, one or two or more types can be selected from styrene, α-methylstyrene, vinyltoluene, and p-tertiarybutylstyrene, and styrene is particularly preferable. . Further, as the conjugated diene compound before hydrogenation constituting the hydrogenated conjugated diene compound, for example, one or more of butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and the like are used. Two or more are selected, and butadiene, isoprene and combinations thereof are particularly preferable. The polymer block mainly composed of the conjugated diene compound before hydrogenation can arbitrarily select the microstructure in the block. For example, in the polybutadiene block, the 1,2-microstructure is 20-50. %, Preferably 25 to 45%.
[0048]
The number average molecular weight of the hydrogenated styrenic block copolymer used in the present invention having the above structure is 5,000 to 1,000,000, preferably 10,000 to 800,000, and more preferably 30,000 to 30,000. The molecular weight distribution [ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn)] is in the range of 500,000. Furthermore, the molecular structure of the hydrogenated block copolymer may be linear, branched, radial, or any combination thereof.
[0049]
The production method of these block copolymers may be obtained by any production method as long as it has the above structure. For example, a vinyl aromatic compound-conjugated diene compound block copolymer is synthesized in an inert solvent using a lithium catalyst or the like by a method described in Japanese Patent Publication No. 40-23798, and then the vinyl aromatic compound is synthesized. As a method for producing a hydrogenated product of a conjugated diene compound block copolymer, for example, it can be obtained by the method described in JP-B-42-8704 and JP-B-43-6636. A hydrogenated block copolymer synthesized using a titanium-based hydrogenation catalyst that exhibits excellent performance in weather resistance and heat deterioration resistance of the hydrogenated block copolymer is preferred. For example, JP-A-59-133203, Hydrogenation for use in the present invention is carried out by hydrogenation in the presence of a titanium-based hydrogenation catalyst in an inert solvent by the method described in JP-A-60-79005. It can be synthesized locking copolymer.
[0050]
At that time, at least 80% of the aliphatic double bond based on the conjugated diene compound of the vinyl aromatic compound-conjugated diene compound block copolymer is hydrogenated to form a polymer block mainly composed of the conjugated diene compound. It can be converted to an olefinic compound polymer block. Hydrogen of aromatic double bond based on vinyl aromatic compound copolymerized with polymer block A mainly composed of vinyl aromatic compound and polymer block B mainly composed of conjugated diene compound if necessary Although there is no restriction | limiting in particular about an addition rate, It is preferable to make a hydrogenation rate into 20% or less. The amount of the unhydrogenated aliphatic double bond contained in the hydrogenated block copolymer can be easily known with an infrared spectrophotometer, a nuclear magnetic resonance apparatus or the like.
[0051]
In the present invention, the thermoplastic elastomer of component (D) is 1 to 100 parts by weight, preferably 100 parts by weight of resin composition for food containers (component (A) + component (B) + component (C)), preferably 10 to 90 parts by weight are blended. When the blending amount of component (D) is less than 1 part by weight with respect to 100 parts by weight of the resin composition for food containers (component (A) + component (B) + component (C)), the tensile elongation at break is high. On the other hand, if the amount exceeds 100 parts by weight, the chemical resistance and flame retardancy are lowered, so neither is preferred.
[0052]
Additive
The resin composition for food containers of the present invention includes the resin composition for food containers as long as the physical properties are not impaired in addition to the components (A) to (C) or the components (A) to (D). Other resins, conventional additives such as pigments, dyes, flame retardant aids, reinforcing agents (glass fibers, carbon fibers, whiskers, etc.), fillers (carbon black, silica, titanium oxide) , Mica, talc, calcium carbonate, potassium titanate, wollastonite, etc.), heat-resisting agent, antioxidant, weathering agent, UV absorber, light stabilizer, lubricant, mold release agent, nucleating agent, plasticizer ( Oil, low molecular weight polyethylene, epoxidized soybean oil, polyethylene glycol, fatty acid esters, etc.), fluidity improver, antistatic agent, compatibilizer (maleic anhydride, dicarboxylic acid such as citric acid and its Anhydride, etc.), and the like may be added to the antimicrobial agent.
[0053]
Light stabilizers and ultraviolet absorbers such as hindered amine compounds, benzoate compounds, benzotriazoles, benzophenones, and formamidines are effective for imparting and improving weather resistance. In addition, nucleating agents, for example, inorganic nucleating agents such as talc, or organic nucleating agents such as aromatic carboxylic acid metal salts, sorbitol or aromatic phosphate metal salts, impart rigidity and scratch resistance. It is effective for improvement.
[0054]
Resin composition for food containers and method for producing molded article
There is no restriction | limiting in particular in the method for manufacturing the resin composition for food containers of this invention, It can manufacture by various methods using said each component. However, the melt kneading method is preferred. Although a small amount of solvent can be used during melt-kneading, it is generally not necessary. Examples of the melt kneader include a single screw extruder, a twin screw extruder, a Banbury mixer, a roll mixer, a kneader, a Brabender plastograph, etc., and a melt kneading method using a twin screw extruder is most preferable. . The melt kneading temperature is not particularly limited, but is usually in the range of 150 to 350 ° C.
[0055]
A food container is molded by injection molding using the resin composition for a food container of the present invention thus obtained.
[0056]
As a molded object shape | molded with the resin composition for food containers of this invention, a platter, a plate, a tray, a bowl, a cup, a lid | cover etc. can be mentioned other than a general food container, for example. In particular, as a food container molded with the resin composition for food containers of the present invention, even when edible oil is adhered during heating in a microwave oven, the food container is not thermally damaged or deformed, for example, It is preferably used for a transparent lid such as a lunch box or a main body container such as a lunch box. The main body container such as a lunch box may be non-foamed or foamed.
[0057]
【Example】
In order to describe the resin composition for food containers of the present invention in more detail, the present invention will be specifically described below with reference to examples. However, the present invention is limited by this unless departing from the spirit of the present invention. is not
In the examples, the following resins were used.
[0058]
Component (A): PPE resin: Poly (2,6-dimethyl-1,4-phenylene) ether (trademark; PPO640, Nippon G Plastics Co., Ltd.) having an intrinsic viscosity (chloroform, 25 ° C.) of 0.40 dl / g Company-made),
Component (B): Syndiotactic styrene polymer (s-PS): molecular weight 180,000¹³Syndiotactic polystyrene (trademark; Zalec 130ZC, manufactured by Idemitsu Petrochemical Co., Ltd.) having a syndiotacticity of 98% expressed by a racemic pentad ratio by C-NMR analysis,
Component (C): Styrenic resin (PS): High impact styrene resin (HIPS) (trademark; 870ST, manufactured by Nippon Polystyrene Corporation).
[0059]
Examples 1-2 and Comparative Examples 1-2
Each component in the ratio (parts by weight) shown in Table 1 was melt-kneaded using a 30 mm twin screw extruder at a kneading temperature of 280 ° C. and a rotation speed of 280 rpm to prepare pellets. Using this pellet, a test piece was prepared by injection molding under the conditions of a temperature of 280 ° C. and a mold temperature of 60 ° C.
[0060]
Further, a molded product imitating a 0.5 mm thick food container was press-molded at a temperature of 280 ° C. using the obtained pellets. A test piece having a width of 12.7 mm and a length of 75 mm was cut out from this sheet to obtain a test piece for oil resistance evaluation.
[0061]
The following characteristics evaluation was performed about the obtained test piece. The results are shown in Table 1.
[0062]
Below, the measuring method used for characteristic evaluation is described.
(1) Heat deflection temperature (HDT): Measured according to ASTM D648.
(2) Tensile strength (TS): Measured according to ASTM D638.
(3) Chemical resistance: The 0.5 mm thickness test piece prepared above is bent and fixed in a state where a strain of 0.6% is applied to the surface (FIG. 1), and salad oil is applied to the surface to output 500 W. For 90 seconds in a microwave oven. Subsequent state changes were observed.
[0063]
As the evaluation criteria, the case where the test piece did not break under the above-mentioned conditions was rated as ◯, and the case where the break occurred was marked as x.
[0064]
[Table 1]

[0065]
【The invention's effect】
The molded article molded from the resin composition for food containers of the present invention is excellent in heat resistance, in particular, excellent in oil resistance (chemical resistance) at high temperatures, and also has good melting characteristics, workability and impact resistance. Therefore, it is extremely useful as a food container for frozen / microwave ovens and a container for high fat foods.
[Brief description of the drawings]
[Fig.1] Chemical resistance test method

Claims (4)

(A) 5 to 90 parts by weight of a polyphenylene ether resin, (B) 10 to 95 parts by weight of a syndiotactic styrene polymer, and (C) 0 to 85 parts by weight of a styrene resin (provided that component (A) + component ( B) + component (C) = 100 parts by weight). A resin composition for food containers. The resin composition for food containers, further comprising (D) 1 to 100 parts by weight of a thermoplastic elastomer with respect to 100 parts by weight of the resin composition for food containers according to claim 1. The polyphenylene ether resin of component (A) is a poly (2,6-dimethyl-1,4-polysiloxane having an intrinsic viscosity in the range of 0.08 to 0.60 dl / g measured at 25 ° C. using chloroform as a solvent. The resin composition for food containers according to claim 1, wherein the resin composition is phenylene) ether. The resin composition for food containers according to claim 2 or 3, wherein the thermoplastic elastomer of component (D) is a block copolymer of styrene and butadiene or styrene and isoprene, or a hydrogenated product thereof. object.

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