JP4348943B2 - Heat-sealing material for easy-open container and easy-open container using the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、充分な封着力を有すると共に、開封時の開封が容易、且つ耐熱性をも有する熱封着部を形成することができる易開封性容器用熱封着材及びそれを用いた易開封性容器に関し、特に、プロピレン系樹脂を熱封着面に有する包装容器又は包装袋等に好適に用いられる易開封性容器用熱封着材及びそれを用いた易開封性容器に関する。
【０００２】
【従来の技術】
従来より、樹脂容器本体を樹脂フィルム状蓋材で熱封着して包装するシールパック包装が、乳製品、菓子、果汁飲料等の主に飲食品の包装に盛んに用いられており、樹脂包装袋と共に重要な地位を占めるに到っている。そして、それらの熱封着材としては、従来より溶液型接着剤やホットメルト型接着剤が用いられてきたが、これらは、開封時に熱封着材が延性破壊を起こして糸状物を形成するため、開封が必ずしも容易ではなかったり、剥離面の外観が良くない等の易開封性に欠けるという問題があり、又、耐熱性不足のために、高温下で剥離してしまう等の封着性に欠けるという問題があった。
【０００３】
こうした問題を改良すべく、封着性と易開封性を兼ね備えた熱封着材が、種々提案され、用いられている。例えば、エチレン−酢酸ビニル共重合体に粘着付与剤を配合した組成物があり、又、オレフィン系重合体を芳香族ビニル単量体で改質した改質オレフィン系重合体を主成分とする材料（例えば、特許文献１参照。）等がある。しかしながら、これらの熱封着材を用いた包装容器又は包装袋等も、内容物を充填し、例えば１３５℃程度の高温で殺菌処理するとか、電子レンジで温める等の高温雰囲気下において、熱封着部でへたりやしわ、ひいては浮きや剥離等が往々にして発生するという問題があった。更に、この耐熱性の問題に対して、プロピレン系樹脂を芳香族ビニル単量体で改質した改質プロピレン系樹脂を主成分とする熱封着材を、プロピレン系樹脂を熱封着面に有する包装容器等の該プロピレン系樹脂面に熱封着した易開封性容器等も提案されている（例えば、特許文献２、特許文献３参照。）。
【０００４】
【特許文献１】
特公平１−４２９６７号公報。
【特許文献２】
特開平１１−１００４８３号公報。
【特許文献３】
特開２０００−１７７０７９号公報。
【０００５】
しかしながら、本発明者等の検討によると、それらに開示される易開封性容器と言えども、封着性と開封性とのバランスにおいて改良の余地を残すものであることが判明した。
【０００６】
【発明が解決しようとする課題】
本発明は、易開封性容器用熱封着材及び易開封性容器における前述の従来技術に鑑みてなされたものであって、従って、本発明は、充分な封着力を有すると共に、開封時の開封が容易、且つ耐熱性をも有する熱封着部を形成することができる易開封性容器用熱封着材及びそれを用いた易開封性容器を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明者等は、前述の課題を解決すべく鋭意検討した結果、特定の改質プロピレン系重合体を用いることにより、前記目的を達成できることを見出し本発明を完成したもので、即ち、本発明は、下記の条件（１）、（２）、及び（３）を満足するプロピレン系重合体３０〜９５重量％とビニル単量体７０〜５重量％をグラフト反応条件に付して得られた改質プロピレン系重合体を含有する易開封性容器用熱封着材、及び、該易開封性容器用熱封着材とプロピレン系樹脂表面とが熱封着されてなる熱封着構造を有する易開封性容器、を要旨とする。
【０００８】
（１）プロピレンの含有量が８５〜９５重量％、エチレンを含む炭素数２〜８の他のα−オレフィンの含有量が１５〜５重量％であること〔ここで、「重量％」は、プロピレンと、エチレンを含む炭素数２〜８の他のα−オレフィンとの合計量に対するものである。〕。
（２）室温キシレン可溶分の含有量が１０〜９０重量％であること。
（３）エチレンを含む炭素数２〜８の他のα−オレフィンの含有量〔Ｙ；重量％〕と室温キシレン可溶分の含有量〔ＣＸＳ；重量％〕とが、下式の関係を有すること。
０≦５Ｙ−２５＜ＣＸＳ
【０００９】
【発明の実施の形態】
本発明の易開封性容器用熱封着材を構成する改質プロピレン系重合体におけるプロピレン系重合体は、下記の条件（１）、（２）、及び（３）を満足するものである。
（１）プロピレンの含有量が８５〜９５重量％、エチレンを含む炭素数２〜８の他のα−オレフィンの含有量が１５〜５重量％であること〔ここで、「重量％」は、プロピレンと、エチレンを含む炭素数２〜８の他のα−オレフィンとの合計量に対するものである。〕。
（２）室温キシレン可溶分の含有量が１０〜９０重量％であること。
（３）エチレンを含む炭素数２〜８の他のα−オレフィンの含有量〔Ｙ；重量％〕と室温キシレン可溶分の含有量〔ＣＸＳ；重量％〕とが、下式の関係を有すること。
０≦５Ｙ−２５＜ＣＸＳ
【００１０】
ここで、条件（１）における炭素数２〜８の他のα−オレフィンとしては、例えば、エチレン、１−ブテン、３−メチル−１−ブテン、１−ペンテン、４−メチル−１−ペンテン、１−ヘキセン、１−オクテン等が挙げられ、これらの中で、本発明におけるプロピレン系重合体として、プロピレンとエチレンとからなるものが好ましい。
【００１１】
そして、本発明におけるプロピレン系重合体は、条件（１）において、プロピレンの含有量が８５〜９５重量％、エチレンを含む炭素数２〜８の他のα−オレフィンの含有量が１５〜５重量％であることが必須であり、プロピレンの含有量が８７〜９５重量％、他のα−オレフィンの含有量が１３〜５重量％であるのが好ましく、プロピレンの含有量が８８〜９２重量％、他のα−オレフィンの含有量が１２〜８重量％であるのが特に好ましい。プロピレンの含有量が前記範囲未満で、他のα−オレフィンの含有量が前記範囲超過では、易開封性容器用熱封着材として耐熱性が劣り、一方、プロピレンの含有量が前記範囲超過で、他のα−オレフィンの含有量が前記範囲未満では、易開封性容器用熱封着材として開封性が劣ることとなる。
【００１２】
更に、本発明におけるプロピレン系重合体は、条件（２）において、室温キシレン可溶分の含有量が１０〜６０重量％であることが必須であり、３０〜６０重量％であるのが好ましい。室温キシレン可溶分の含有量が前記範囲未満では、易開封性容器用熱封着材として開封性が劣ることとなり、一方、前記範囲超過では、易開封性容器用熱封着材として耐熱性が劣ることとなる。
【００１３】
更に、本発明におけるプロピレン系重合体は、条件（３）において、エチレンを含む炭素数２〜８の他のα−オレフィンの前記含有量〔Ｙ；重量％〕と室温キシレン可溶分の前記含有量〔ＣＸＳ；重量％〕とが、下式の関係を有することが必須であり、下式の関係を有さない場合には、易開封性容器用熱封着材として封着性と開封性のバランスが劣ることとなる。
０≦５Ｙ−２５＜ＣＸＳ
【００１４】
以上の前記条件（１）〜（３）を満足するプロピレン系重合体は、ＪＩＳ Ｋ７２１０に準拠して温度２３０℃、荷重２１．１８Ｎで測定したメルトフローレートが０．１〜５０ｇ／１０分で、示差走査熱量計によってＪＩＳ Ｋ７１２１に準拠して、昇温速度１０℃／分で測定した融点が１６０〜１７０℃であるのが好ましい。又、ＪＩＳ Ｋ７２０３に準拠して測定した曲げ弾性率が１５０〜６００ＭＰａで、ＪＩＳ Ｋ７１１３に準拠して測定した引張破断強度が３０ＭＰａ以上であるのが好ましい。
【００１５】
本発明における前記プロピレン系重合体の製造方法は、前記条件（１）〜（３）を満足する限り特に限定されるものではないが、具体的には、例えば、第一段階でプロピレンを単独重合した後、第二段階でプロピレンとエチレン、或いは更に炭素数４〜８の他のα−オレフィンとを共重合する逐次重合方法、又は、プロピレンとエチレン、或いは更に炭素数４〜８の他のα−オレフィンとを共重合する一段重合方法等が挙げられる。
【００１６】
これらの製造方法の中で、本発明におけるプロピレン系重合体としては、逐次重合方法によるのが好ましく、その逐次重合方法について更に詳述すると、この逐次重合に用いられる触媒は、有機アルミニウム化合物と、チタン原子、マグネシウム原子、ハロゲン原子、及び電子供与性化合物を必須とする固体成分とからなるものが好適である。
【００１７】
ここで、有機アルミニウム化合物としては、この種の重合において公知の、一般式Ｒ1 m ＡｌＸ3-m （式中、Ｒ1 は炭素数１〜１２の炭化水素残基、Ｘはハロゲン原子を示し、ｍは１〜３の数である。）で表される化合物、例えば、トリメチルアルミニウム、トリエチルアルミニウム等のトリアルキルアルミニウム、ジメチルアルミニウムクロリド、ジエチルアルミニウムクロリド等のジアルキルアルミニウムハライド、メチルアルミニウムセスキクロリド、エチルアルミニウムセスキクロリド等のアルキルアルミニウムセスキハライド、メチルアルミニウムジクロリド、エチルアルミニウムジクロリド等のアルキルアルミニウムジハライド、ジエチルアルミニウムハイドライド等のアルキルアルミニウムハイドライド等が挙げられる。
【００１８】
又、チタン原子、マグネシウム原子、ハロゲン原子、及び電子供与性化合物を必須とする固体成分としては、やはりこの種の重合において公知であって、チタン原子の供給源となるチタン化合物としては、一般式Ｔｉ（ＯＲ2 ）4-n Ｘn （式中、Ｒ2 は炭素数１〜１０の炭化水素残基、Ｘはハロゲン原子を示し、ｎは０〜４の数である。）で表される化合物が挙げられ、中で、四塩化チタン、テトラエトキシチタン、テトラブトキシチタン等が好ましく、マグネシウム原子の供給源となるマグネシウム化合物としては、例えば、ジアルキルマグネシウム、マグネシウムジハライド、ジアルコキシマグネシウム、アルコキシマグネシウムハライド等が挙げられ、中でマグネシウムジハライド等が好ましい。尚、ハロゲン原子としては、弗素、塩素、臭素、沃素が挙げられ、中で、塩素が好ましく、これらは、通常、前記チタン化合物或いはマグネシウム化合物から供給されるが、アルミニウムのハロゲン化物、珪素のハロゲン化物、タングステンのハロゲン化物等の他のハロゲン供給源から供給されてもよい。
【００１９】
電子供与性化合物としては、アルコール類、フェノール類、ケトン類、アルデヒド類、カルボン酸類、有機酸又は無機酸及びその誘導体等の含酸素化合物、アンモニア、アミン類、ニトリル類、イソシアネート類等の含窒素化合物等が挙げられ、中で、無機酸エステル、有機酸エステル、有機酸ハライド等が好ましく、珪酸エステル、フタル酸エステル、酢酸セロソルブエステル、フタル酸ハライド等が更に好ましく、一般式Ｒ3 Ｒ4 3-p Ｓｉ（ＯＲ5 ）p （式中、Ｒ3 は炭素数３〜２０、好ましくは４〜１０の分岐状脂肪族炭化水素残基、又は、炭素数５〜２０、好ましくは６〜１０の環状脂肪族炭化水素残基を示し、Ｒ4 は炭素数１〜２０、好ましくは１〜１０の分岐又は直鎖状脂肪族炭化水素残基を示し、Ｒ5 は炭素数１〜１０、好ましくは１〜４の脂肪族炭化水素残基を示し、ｐは１〜３の数である。）で表される有機珪素化合物、例えば、ｔ−ブチル−メチル−ジメトキシシラン、ｔ−ブチル−メチル−ジエトキシシラン、シクロヘキシル−メチル−ジメトキシシラン、シクロヘキシル−メチル−ジエトキシシラン等が特に好ましい。
【００２０】
本発明におけるプロピレン系重合体の逐次重合方法は、第一段階で、プロピレンを供給して、前記触媒の存在下に温度５０〜１５０℃、好ましくは５０〜１００℃、プロピレンの分圧０．５〜４．５ＭＰａ、好ましくは１．０〜３．５ＭＰａの条件で、プロピレンの単独重合を実施し、引き続いて、第二段階で、プロピレンとエチレン、又は、プロピレンとエチレンと炭素数４〜８のα−オレフィンを供給して、前記触媒の存在下に温度５０〜１５０℃、好ましくは５０〜１００℃、プロピレン及びエチレンの分圧各０．３〜４．５ＭＰａ、好ましくは０．５〜３．５ＭＰａの条件で、プロピレンとエチレンとの共重合、又は、プロピレンとエチレンと他のα−オレフィンとの共重合を実施することによりなされる。
【００２１】
尚、その際の重合は、回分式、連続式、半回分式のいずれによってもよく、第一段階及び第二段階の重合共、気相又は液相中で実施するのが好ましく、第二段階の重合は気相中で実施するのが特に好ましい。各段階の滞留時間は各々０．５〜１０時間、好ましくは１〜５時間とする。
【００２２】
又、前記方法により製造されるプロピレン系重合体の粉体粒子にベタツキ等をなくして流動性を付与するために、第一段階での(i) 成分の重合後、第二段階での(ii)成分の重合開始前又は重合途中に、活性水素含有化合物を、触媒の固体成分中のチタン原子に対して１００〜１０００倍モルで、且つ、触媒の有機アルミニウム化合物に対して２〜５倍モルの範囲で添加することが好ましい。ここで、その活性水素含有化合物としては、例えば、水、アルコール類、フェノール類、アルデヒド類、カルボン酸類、酸アミド類、アンモニア、アミン類等が挙げられる。
【００２３】
尚、以上の本発明におけるプロピレン系重合体は、優れた柔軟性、透明性及びプロピレン単独重合体と同等レベルの耐熱性を有し、かつ引張強度や耐衝撃性等の機械的物性に優れたプロピレン共重合体として、例えば、特開２００１−２２６４３５号公報等によって知られているものである。
【００２４】
又、本発明の易開封性容器用熱封着材を構成する改質プロピレン系重合体におけるビニル単量体としては、例えば、スチレン、α−メチルスチレン、２−メチルスチレン、３−メチルスチレン、４−メチルスチレン、ジメチルスチレン、クロロスチレン等の芳香族ビニル化合物類、酢酸ビニル、プロピオン酸ビニル等のビニルエステル類、（メタ）アクリル酸〔ここで、「（メタ）アクリル」とは、「アクリル」又は／及び「メタクリル」を意味するものとする。〕、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ｉ−プロピル（メタ）アクリレート、ｎ−ブチル（メタ）アクリレート、ｓｅｃ−ブチル（メタ）アクリレート、ヘキシル（メタ）アクリレート、２−エチルヘキシル（メタ）アクリレート、オクチル（メタ）アクリレート、ドデシル（メタ）アクリレート、グリシジル（メタ）アクリレート等の（メタ）アクリル酸又はそのエステル類、無水マレイン酸、ジメチルマレエート、ジ（２−エチルヘキシル）マレエート等の他の不飽和カルボン酸又はそのエステル類、（メタ）アクリロニトリル等の不飽和ニトリル類、塩化ビニル、塩化ビニリデン等の不飽和モノ又はジハライド類等を挙げることができ、中で、芳香族ビニル化合物類が好ましく、スチレン、２−メチルスチレンが特に好ましく、就中、スチレンが好ましい。尚、本発明において、これらのビニル単量体は２種以上が併用されていてもよい。
【００２５】
本発明において、改質プロピレン系重合体は、前記プロピレン系重合体３０〜９５重量％、好ましくは４０〜７０重量％、特に好ましくは４５〜６５重量％と、前記ビニル単量体７０〜５重量％、好ましくは６０〜３０重量％、特に好ましくは５５〜３５重量％をグラフト反応条件に付して得られたものであり、ビニル単量体がこの範囲未満では、熱封着材として封着力が強過ぎて易開封性容器としての開封が困難となり、一方、この範囲超過では、均質性が損なわれ実用に供し得ない。
【００２６】
又、本発明において、グラフト反応条件としては、基本的には、従来公知の溶融混練下、溶液下、水性懸濁下等での、電子線照射或いはラジカル発生剤添加等による方法を採り得るが、本発明においては、ラジカル発生剤添加での水性懸濁法によるのが好ましい。
【００２７】
ラジカル発生剤添加での水性懸濁法について、具体的に述べれば、ラジカル発生剤としては、分解温度が好ましくは５０℃以上、特に好ましくは５０〜１３０℃であって、油溶性であるものが好ましい。分解温度が５０℃未満のものでは、ビニル単量体の重合が異常に進行して均質な改質重合体が得られにくい傾向となる。尚、ここで、分解温度とは、ベンゼン１リットル中にラジカル発生剤０．１モルを添加して１０時間放置したときにラジカル発生剤の５０％が分解するときの温度、所謂、「１０時間半減期温度」である。
【００２８】
本発明において、そのラジカル発生剤としては、例えば、２，４−ジクロロベンゾイルパーオキサイド（分解温度５３℃）、ｔ−ブチルパーオキシピバレート（分解温度５５℃）、３，５，５−トリメチルヘキサノイルパーオキサイド（分解温度５９．５℃）、オクタノイルパーオキサイド（分解温度６２℃）、ｔ−ブチルパーオキシ−２−エチルヘキサノエート（分解温度７２．５℃）、ｏ−メチルベンゾイルパーオキサイド（分解温度７３℃）、ベンゾイルパーオキサイド（分解温度７４℃）、シクロヘキサノンパーオキサイド（分解温度９７℃）、２，５−ジメチル−２，５−ジ（ベンゾイルパーオキシ）ヘキサン（分解温度１００℃）、ｔ−ブチルパーオキシベンゾエート（分解温度１０４℃）、ジ−ｔ−ブチル−ジパーオキシフタレート（分解温度１０７℃）、メチルエチルケトンパーオキサイド（分解温度１０９℃）、ジクミルパーオキサイド（分解温度１１７℃）、ジ−ｔ−ブチルパーオキサイド（分解温度１２４℃）等の有機過酸化物、アゾビス（２，４−ジメチルバレロニトリル）（分解温度５２℃）、アゾビスイソブチロニトリル（分解温度７９℃）等のアゾ化合物等が挙げられる。尚、本発明において、これらのラジカル発生剤は２種以上が併用されていてもよい。
【００２９】
前記ラジカル発生剤の添加量は、前記ビニル単量体の使用量１００重量部に対して０．０１〜１０重量部程度であり、この範囲より少ないと反応が円滑に進まず、この範囲より多いと改質重合体中にゲルが発生し易い傾向となる。
【００３０】
本発明において好適な水性懸濁グラフト反応条件としては、前記プロピレン系重合体、前記ビニル単量体、及び前記ラジカル発生剤の所定量を含む水性懸濁液を、ラジカル発生剤の分解が実質的に起こらない温度に昇温してビニル単量体をプロピレン系重合体に含浸させた後、更に昇温してグラフト反応を完結させた方法である。
【００３１】
ここで、水性懸濁液は、プロピレン系重合体の水性懸濁液に、ラジカル発生剤を溶存させたビニル単量体を加えて攪拌するか、ラジカル発生剤を溶存させたビニル単量体の水性懸濁液に、プロピレン系重合体を加えて攪拌するいずれかの方法によって作製するのが好ましい。
【００３２】
又、その水性懸濁液中のプロピレン系重合体及びビニル単量体の含有量は、水１００重量部に対して５〜１００重量部程度であり、安定な分散状態を保つために、例えば、ポリビニルアルコール、メチルセルロース、ヒドロキシセルロース等の水溶性高分子、アルキルベンゼンスルホネート等の陰イオン性界面活性剤、ポリオキシエチレンアルキルエーテル等の非イオン性界面活性剤、或いは、酸化マグネシウム、燐酸カルシウム等の水不溶性の無機塩等の懸濁安定剤を、単独で又は併用して、水１００重量部に対して０．０１〜１０重量部程度用いることが好ましい。
【００３３】
プロピレン系重合体へのビニル単量体の含浸は、攪拌下、一般的には室温〜１００℃、好ましくは７０〜１００℃で、遊離のビニル単量体がビニル単量体全量の２０重量％以下、好ましくは５重量％以下となる程度まで、通常は２〜８時間程度でなされる。プロピレン系重合体はビニル単量体と比較的相溶性があるので、反応開始前にこの程度のビニル単量体が遊離していても、反応中にこれらのビニル単量体はプロピレン系重合体に含浸し、均質な改質重合体が得られる。
【００３４】
グラフト反応は、一般的には、攪拌下、５０〜１５０℃程度の温度、常圧〜１ＭＰａ程度の圧力で、２〜１０時間程度でなされるが、その間の温度及び圧力は、一定である必要はない。尚、反応に用いられるプロピレン系重合体は、粉粒状で用いられるが、平均粒径が１〜８ｍｍ、特には３〜７ｍｍの粒子状であるのが好ましい。
【００３５】
本発明において、改質プロピレン系重合体としては、熱封着材としての封着力と易開封性の面から、前記プロピレン系重合体のマトリックスに、前記ビニル単量体の重合体が０．２〜３μｍの粒子径で粒子分散し、その界面に前記ビニル単量体がグラフト重合したプロピレン系重合体が存在する分散構造を有するものが好ましい。
【００３６】
以上の改質プロピレン系重合体を含有する本発明の易開封性容器材は、易開封性を向上させること等を目的として、更に、前記改質プロピレン系重合体以外のオレフィン系重合体、又は／及び、前記改質プロピレン系重合体以外のビニル単量体の重合体を含有していてもよい。
【００３７】
ここで、そのオレフィン系重合体としては、例えば、エチレン、プロピレン、１−ブテン等の炭素数２〜８程度のα−オレフィンの単独重合体、それらのα−オレフィンと、エチレン、プロピレン、１−ブテン、３−メチル−１−ブテン、１−ペンテン、４−メチル−１−ペンテン、４，４−ジメチル−１−ペンテン、１−ヘキセン、４−メチル−１−ヘキセン、１−ヘプテン、１−オクテン、１−デセン、１−オクタデセン等の炭素数２〜１８程度の他のα−オレフィンや、酢酸ビニル、（メタ）アクリル酸、（メタ）アクリル酸エステル等との共重合体等が挙げられ、具体的には、例えば、分岐状低密度ポリエチレン、直鎖状高密度ポリエチレン等のエチレン単独重合体、エチレン−プロピレン共重合体、エチレン−１−ブテン共重合体、エチレン−プロピレン−１−ブテン共重合体、エチレン−４−メチル−１−ペンテン共重合体、エチレン−１−ヘキセン共重合体、エチレン−１−オクテン共重合体等の直鎖状低・中・高密度エチレン−α−オレフィン共重合体、及び、エチレン−酢酸ビニル共重合体、エチレン−（メタ）アクリル酸共重合体、エチレン−（メタ）アクリル酸エチル共重合体等のエチレン系樹脂、プロピレン単独重合体、プロピレン−エチレン共重合体、プロピレン−エチレン−１−ブテン共重合体等のプロピレン系樹脂、及び、１−ブテン単独重合体、１−ブテン−エチレン共重合体、１−ブテン−プロピレン共重合体等の１−ブテン系樹脂等が挙げられる。中で、分岐状低密度ポリエチレンが特に好ましい。尚、本発明において、これらのオレフィン系重合体は２種以上が併用されていてもよい。
【００３８】
又、そのビニル単量体の重合体としては、前記改質プロピレン系重合体において挙げたビニル単量体と同様のビニル単量体の重合体及び共重合体が挙げられ、中で、ポリスチレンが特に好ましい。
【００３９】
本発明において、前記改質プロピレン系重合体以外に含有されるこれらのオレフィン系重合体又は／及びビニル単量体の重合体の含有量は、改質プロピレン系重合体１００重量部に対して、両者の合計量として８００重量部以下であるのが好ましく、１〜６００重量部であるのが特に好ましい。
【００４０】
前記改質プロピレン系重合体、又は、更に前記改質プロピレン系重合体以外の前記オレフィン系重合体、又は／及び、前記改質プロピレン系重合体以外のビニル単量体の重合体を含有する本発明の易開封性容器用熱封着材において、プロピレン系重合体の前記改質時に生成したビニル単量体のグラフト及びホモ重合体、並びに、更に含有させた前記ビニル単量体の重合体の全含有量は、５〜７０重量％であるのが好ましく、６〜６０重量％であるのが更に好ましく、７〜５０重量％であるのが特に好ましい。ビニル単量体の重合体の全含有量がこの範囲未満では、熱封着材として封着力が強過ぎて開封が困難な傾向となり、一方、この範囲超過では、均質性が損なわれ実用に供し得ない。
【００４１】
尚、本発明の易開封性容器用熱封着材には、前記改質プロピレン系重合体、前記改質プロピレン系重合体以外のオレフィン系重合体又は／及び前記改質プロピレン系重合体以外のビニル単量体の重合体の外に、本発明の効果を損なわない範囲で、これら以外の熱可塑性樹脂やゴム、及び、酸化防止剤、紫外線吸収剤、光安定剤、帯電防止剤、ブロッキング防止剤、滑剤、可塑剤、顔料等の添加剤、充填材等が配合されていてもよい。これらの配合は、改質に供するプロピレン系重合体に予め加えておくとか、改質プロピレン系重合体以外のオレフィン系重合体や改質プロピレン系重合体以外のビニル単量体重合体に加えておくとか、熱封着材の調製時に加えるとかの外、改質プロピレン系重合体の製造時に、例えば、ビニル単量体にラジカル発生剤と共に加える等の方法によってもよい。
【００４２】
本発明の易開封性容器用熱封着材は、前記改質プロピレン系重合体、必要に応じて用いられる前記オレフィン系重合体又は／及び必要に応じて用いられる前記ビニル単量体の重合体、並びに、他の熱可塑性樹脂やゴム、添加剤等を、タンブラーブレンダー、リボンブレンダー、Ｖ型ブレンダー、ヘンシェルミキサー等により均一に混合した後、一軸又は二軸押出機、ロール、バンバリーミキサー、ニーダー、ブラベンダー等により溶融混練することにより調製される。
【００４３】
本発明の易開封性容器用熱封着材は、その熱封着材単層で、易開封性容器としての容器蓋体或いは容器本体に用いられてもよいが、実用上は、例えば、ポリアミド系樹脂、ポリエステル系樹脂、エチレン−酢酸ビニル共重合体鹸化物、ポリカーボネート系樹脂、ポリスチレン系樹脂、アクリル系樹脂、ポリオレフィン系樹脂等の各種熱可塑性樹脂のフィルム、アルミニウム箔、紙等の基材との積層体として用いられ、その積層方法としては、グルーラミネート法、押出ラミネート法、及び前記各種熱可塑性樹脂との共押出法等の従来公知の方法が採られる。尚、その際の本発明の熱封着材層の厚みは、５〜１００μｍ程度とするのが好ましい。
【００４４】
本発明の易開封性容器は、前記易開封性容器用熱封着材と被着材表面とが熱封着されてなる熱封着構造を有するものである。その被着材としては、特に限定されるものではないが、プロピレン系樹脂であるのが好ましく、そのプロピレン系樹脂としては、前記改質プロピレン系重合体以外のオレフィン系重合体として挙げたと同様のプロピレン系樹脂が挙げられ、そのプロピレン系樹脂が表面を形成しているものであれば、単層或いは積層状態のいずれでも構わない。
【００４５】
本発明において、具体的な易開封性容器の形態を、被着材をプロピレン系樹脂として挙げれば、例えば、（１）容器本体と蓋材からなる包装容器として、（ａ）本発明の易開封性容器用熱封着材を蓋材側に用いた場合であって、プロピレン系樹脂を熱封着面に有する容器本体と、該熱封着材を熱封着面に有する蓋材とからなる易開封性容器、（ｂ）本発明の易開封性容器用熱封着材を容器本体側に用いた場合であって、該熱封着材を熱封着面に有する容器本体と、プロピレン系樹脂を熱封着面に有する蓋材とからなる易開封性容器、（２）包装袋として、（ａ）本発明の易開封性容器用熱封着材を袋の両面に用いた場合であって、該熱封着材を熱封着面に有する袋部材の熱封着材同士を対向させて熱封着した袋体である易開封性容器、及び、（ｂ）本発明の易開封性容器用熱封着材を袋の一方の面に用い、他方の面にプロピレン系樹脂を熱封着面に有する袋部材を用いた場合であって、該熱封着材を熱封着面に有する袋部材と、プロピレン系樹脂を熱封着面に有する袋部材のプロピレン系樹脂表面とを熱封着した袋体である易開封性容器、等が挙げられる。
【００４６】
【実施例】
以下、本発明を実施例によりさらに具体的に説明するが、本発明はその要旨を越えない限り、以下の実施例に限定されるものではない。尚、実施例に用いた改質プロピレン系重合体を以下に示す。
【００４７】
〔改質プロピレン系重合体の製造〕
＜固体成分触媒の製造＞
窒素置換した内容積５０リットルの攪拌機付槽に脱水及び脱酸素したｎ−ヘプタン２０リットルを導入し、次いで、塩化マグネシウム４モルとテトラブトキシチタン８モルとを導入して９５℃で２時間反応させた後、温度を４０℃に下げ、メチルヒドロポリシロキサン（粘度２０センチストークス）４８０ミリリットルを導入して更に３時間反応させた後、反応液を取り出し、生成した固体成分をｎ−ヘプタンで洗浄した。次いで、前記攪拌機付槽を用いて該槽に脱水及び脱酸素したｎ−ヘプタン１５リットルを導入し、次いで、得られた固体成分をマグネシウム原子換算で３モル導入し、更に、四塩化珪素８モルをｎ−ヘプタン２５ミリリットルに加えた混合液を３０℃で３０分間かけて導入して、温度を９０℃に上げ、１時間反応させた後、反応液を取り出し、生成した固体成分をｎ−ヘプタンで洗浄した。引き続いて、前記攪拌機付槽を用いて該槽に脱水及び脱酸素したｎ−ヘプタン５リットルを導入し、次いで、前記で得られたチタン含有固体成分２５０ｇと、１，５−ヘキサジエン７５０ｇ、ｔ−ブチル−メチル−ジメトキシシラン１３０ミリリットル、ジビニルジメチルシラン１０ミリリットル、トリエチルアルミニウム２２５ｇとをそれぞれ導入して３０℃で２時間接触させた後、反応液を取り出し、ｎ−ヘプタンで洗浄して固体成分触媒を得た。得られた固体成分触媒は、１，５−ヘキサジエンの予備重合量がチタン含有固体成分当たり２．９７ｇのものであった。
【００４８】
＜プロピレン系重合体の製造＞
内容積５５０リットルの第一段反応器に、温度７０℃で、圧力約３．２ＭＰａになるように、プロピレンと、トリエチルアルミニウム、及び、重合体生成速度が２０ｋｇ／時間となるような量比の前記固体成分触媒とを連続的に供給し、更に、分子量制御剤としての水素を連続的に供給して液相中で重合を実施した（第一段階重合）。引き続いて、生成重合体を、プロピレンパージ槽を経由させて、内容積１９００リットルの第二段反応器に導入し、温度６０℃で、圧力３．０ＭＰａになるように、生成する共重合体中の組成割合に応じたプロピレンとエチレンとを連続的に供給し、更に、分子量制御剤としての水素を連続的に供給すると共に、活性水素化合物（エタノール）を、第一段階で供給した固体成分触媒中のチタン原子に対して２００倍モルで、トリエチルアルミニウムに対して２．５倍モルになるように供給して気相中で重合を実施し、生成重合体を連続的にベッセルに移した後、水分を含んだ窒素ガスを導入して反応を停止させた（第二段階重合）。以上により、プロピレン系重合体としてのプロピレン−エチレン共重合体（Ａ）を製造した。
【００４９】
得られたプロピレン−エチレン共重合体（Ａ）は、以下に示す方法で測定した、エチレンの含有量（Ｙ）が１０．２重量％、室温キシレン可溶分の含有量（ＣＸＳ）が３４．７重量％であり、「５Ｙ−２５」が２６であった。又、メルトフローレートが８ｇ／１０分、融点が１６４．２℃、曲げ弾性率が３１８ＭＰａ、引張破断強度が３６ＭＰａのものであった。
【００５０】
＜エチレンの含有量（Ｙ）＞
赤外分光法により測定した。
＜室温キシレン可溶分の含有量（ＣＸＳ）＞
試料１ｇをキシレン３００ミリリットル中でキシレンの沸点１４０℃で攪拌下に溶解させ、１時間経過後、攪拌を続けながら１時間以内に１００℃まで降温し、次いで、急冷用油浴槽に移して攪拌を続けながら２３±２℃まで急冷させて重合体を析出させ、２０分間以上放置した後、析出物を濾紙で自然濾過し、濾液をエバポレーターで蒸発乾固させ、更に１２０℃で２時間減圧乾燥させ、常温まで放冷し、その重量を測定した。
【００５１】
＜メルトフローレート＞
ＪＩＳ Ｋ７２１０に準拠し、温度２３０℃、荷重２１．１８Ｎにて測定した。
＜融点＞
示差走査熱量計（セイコーインスツルメンツ社製）を用いて、ＪＩＳ Ｋ７１２１に準拠して、昇温速度１０℃／分で融解ピーク温度を測定した。
＜曲げ弾性率＞
ＪＩＳ Ｋ７２０３に準拠し、２３℃で測定した。
＜引張破断強度＞
ＪＩＳ Ｋ７１１３に準拠し、２号ダンベルを用いて、２３℃で、引張速度５０ｍｍ／分にて測定した。
【００５２】
＜改質プロピレン系重合体の製造＞
５０リットル容量のオートクレーブに、水２０ｋｇと、懸濁剤としてドデシルベンゼンスルホン酸ナトリウム０．６ｇと、懸濁助剤として第三燐酸カルシウム０．６ｋｇとを入れて水性媒体とし、これに、前記で得られたプロピレン−エチレン共重合体（Ａ）の平均粒径３〜４ｍｍの粒子６ｋｇを加え、攪拌して水性懸濁液とした。この水性懸濁液に、ラジカル発生剤として３，５，５−トリメチルヘキサノイルパーオキサイド１５．６ｇとベンゾイルパーオキサイド９ｇとを溶解したスチレンモノマー６ｋｇを加え、オートクレーブ内に窒素を導入して系内を０．５ｋｇ／ｃｍ2 に加圧した後、オートクレーブ内を５５℃に昇温し、この温度で６時間攪拌して、ラジカル発生剤を含むスチレンモノマーの全量をプロピレン系重合体粒子中に含浸させた。引き続いて、オートクレーブ内を１００℃に昇温し、この温度で３時間攪拌してグラフト反応を行い、更に１２０℃に昇温し、この温度で１５時間攪拌して反応を完結させた。冷却後、反応固形物を取り出して水洗し、粒子状の改質プロピレン−エチレン共重合体（Ａ’）粒子１２ｋｇを得た。得られた改質プロピレン−エチレン共重合体（Ａ’）は、ポリスチレン５０重量％を含有するものであった。
【００５３】
実施例１〜３
前記で得られた改質プロピレン−エチレン共重合体（Ａ’）のペレットを、或いは、更に、該改質プロピレン−エチレン共重合体１００重量部に対して、低密度ポリエチレン（密度０．９１３ｇ／ｃｍ3 、１９０℃、荷重２１．１８Ｎで測定したメルトフローレート７ｇ／１０分）、又は、ポリスチレン（密度１．１ｇ／ｃｍ3 、２００℃、荷重４９．０３Ｎで測定したメルトフローレート６ｇ／１０分）を表１に示す量で加える場合には、それらを一軸押出機に供給して２１０℃で溶融混練してペレット化したペレットを、Ｔダイを備えた３５ｍｍ径のフィルム成形機（プラコー社製）に供給し、２３０℃で溶融押出して冷却することにより、厚み３０μｍのフィルムを成形し、該フィルムを、イソシアネート系アンカーコート剤を用いて厚み２０μｍのポリエチレンテレフタレートフィルムと接着し２層積層フィルムを作製した。
【００５４】
一方、厚み２００μｍのポリプロピレン樹脂のシートから熱成形して作製した角形の容器本体のフランジ部に、前記の積層フィルムを蓋材として用い、その改質プロピレン−エチレン共重合体層を接着面として、以下に示す条件で熱封着して易開封性容器を作製し、得られた各容器について、以下に示す方法でその剥離強度を測定し、結果を表１に示した。
【００５５】
＜剥離強度＞
熱板式ヒートシーラーを用い、温度１６０℃、１７０℃、１８０℃、又は１９０℃、圧力１．９６×１０5 Ｐａ、時間０．５秒で、蓋材を容器本体フランジ部に５ｍｍ幅で熱圧着し、その接着部を１５ｍｍ長さでサンプリングし、インストロン型引張試験機を用い、長さに直角方向に、２３℃で、引張速度３００ｍｍ／分で剥離することにより１８０度剥離強度（ｇ／１５ｍｍ）を測定した。
【００５６】
更に、前記で得られた各易開封性容器について、以下に示す方法で、熱封着部の耐熱性を評価し、結果を表１に示した。
＜熱封着部の耐熱性＞
易開封性容器を１３５℃に調節したオーブン中に３０分間入れた後、取り出し、熱封着部の外観を目視観察し、以下の基準で評価した。
○；熱封着部にへたり、しわ、浮き、剥離等は認められず。
×；熱封着部にへたり、しわ、浮き、或いは剥離が認められる。
【００５７】
比較例１
プロピレン−エチレン共重合体（Ａ）に代えて、エチレンの含有量が４重量％、室温キシレン可溶分の含有量が０重量％、メルトフローレートが５ｇ／１０分、融点が１４５．１℃、曲げ弾性率が７００ＭＰａ、引張破断強度が３５ＭＰａのプロピレン−エチレン共重合体（Ｂ’）を改質した改質プロピレン−エチレン共重合体（Ｂ’）を用いた外は、実施例１と同様とした。
【００５８】
比較例２
プロピレン−エチレン共重合体（Ａ）に代えて、室温キシレン可溶分の含有量が０重量％、メルトフローレートが８ｇ／１０分、融点が１６４．３℃、曲げ弾性率が１，３００ＭＰａ、引張破断強度が４０ＭＰａのプロピレン単独重合体（Ｃ）を改質した改質プロピレン単独重合体（Ｃ’）を用いた外は、実施例１と同様とした。
【００５９】
【表１】
表１から、比較例１〜２では、熱封着温度１６０℃と１９０℃の間での剥離強度の差は２，５００〜３，５００ｇ／１５ｍｍと大きく、熱封着温度の違いによって、剥離強度が安定せず封着性と開封性とのバランスが劣るのに対して、実施例１〜３では、その差は８００〜１，１００ｇ／１５ｍｍと小さく、熱封着温度の違いによっても、安定した剥離強度を示し封着性と開封性とのバランスが優れ、且つ、耐熱性にも優れていること明らかである。
【００６１】
【発明の効果】
本発明によれば、充分な封着力を有すると共に、開封時の開封が容易、且つ耐熱性をも有する熱封着部を形成することができ、特に、プロピレン系樹脂を熱封着面に有する包装容器又は包装袋等に好適に用いられる易開封性容器用熱封着材及びそれを用いた易開封性容器を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention provides a heat-sealing material for an easily-openable container that has a sufficient sealing force, can be easily opened at the time of opening, and can form a heat-sealing part that also has heat resistance, and an easy-to-use More particularly, the present invention relates to a heat-sealing material for an easily-openable container suitably used for a packaging container or a packaging bag having a propylene-based resin on a heat-sealing surface, and an easily-openable container using the same.
[0002]
[Prior art]
Conventionally, seal pack packaging that heat seals and seals the resin container body with a resin film-like lid material has been actively used for packaging mainly dairy products, confectionery, fruit juice beverages, etc. It has come to occupy an important position with the bag. And as these heat sealing materials, solution type adhesives and hot melt type adhesives have been used conventionally, but these cause the ductile fracture of the heat sealing material at the time of opening to form a filamentous material. Therefore, there is a problem that opening is not always easy or there is a problem of lack of easy opening, such as the appearance of the peeling surface is not good, and sealing properties such as peeling at high temperature due to insufficient heat resistance There was a problem of lacking.
[0003]
In order to improve these problems, various heat sealing materials having both sealing properties and easy opening properties have been proposed and used. For example, there is a composition in which a tackifier is blended with an ethylene-vinyl acetate copolymer, and a material mainly composed of a modified olefin polymer obtained by modifying an olefin polymer with an aromatic vinyl monomer. (For example, refer to Patent Document 1). However, packaging containers or bags using these heat sealing materials are also filled with the contents and heat sealed in a high temperature atmosphere such as sterilizing at a high temperature of about 135 ° C. or warming in a microwave oven. There has been a problem that dripping and wrinkling at the landing part, as well as floating and peeling often occur. Furthermore, with respect to this heat resistance problem, a heat sealing material mainly composed of a modified propylene resin obtained by modifying a propylene resin with an aromatic vinyl monomer is used as a heat sealing surface. An easy-open container such as a packaging container that is heat-sealed to the propylene resin surface has also been proposed (see, for example, Patent Document 2 and Patent Document 3).
[0004]
[Patent Document 1]
Japanese Examined Patent Publication No. 1-4967.
[Patent Document 2]
Japanese Patent Application Laid-Open No. 11-1000048.
[Patent Document 3]
JP 2000-177079 A.
[0005]
However, according to the study by the present inventors, it has been found that even the easy-open containers disclosed therein leave room for improvement in the balance between sealability and openability.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described prior art in the heat-sealing material for easily openable containers and the easily openable containers. Therefore, the present invention has a sufficient sealing force and is capable of being opened. An object of the present invention is to provide a heat-sealing material for an easily-openable container that can be easily opened and that can form a heat-sealing part that also has heat resistance, and an easily-openable container using the same.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by using a specific modified propylene polymer, and thus the present invention has been completed. Was obtained by subjecting 30 to 95% by weight of a propylene polymer satisfying the following conditions (1), (2) and (3) and 70 to 5% by weight of a vinyl monomer to the graft reaction conditions. A heat-sealing material for easily openable containers containing a modified propylene-based polymer, and a heat-sealing structure in which the heat-sealing material for easily-openable containers and a propylene-based resin surface are heat-sealed. The gist is an easily openable container.
[0008]
(1) The content of propylene is 85 to 95% by weight, and the content of other α-olefins having 2 to 8 carbon atoms including ethylene is 15 to 5% by weight [where “% by weight” It is based on the total amount of propylene and other α-olefins having 2 to 8 carbon atoms including ethylene. ].
(2) The content of room temperature xylene solubles is 10 to 90% by weight.
(3) The content of other α-olefins having 2 to 8 carbon atoms including ethylene [Y; wt%] and the room temperature xylene soluble content [CXS; wt%] have the following relationship: thing.
0 ≦ 5Y−25 <CXS
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The propylene-based polymer in the modified propylene-based polymer constituting the heat-sealing material for easily openable containers of the present invention satisfies the following conditions (1), (2), and (3).
(1) The content of propylene is 85 to 95% by weight, and the content of other α-olefins having 2 to 8 carbon atoms including ethylene is 15 to 5% by weight [where “% by weight” It is based on the total amount of propylene and other α-olefins having 2 to 8 carbon atoms including ethylene. ].
(2) The content of room temperature xylene solubles is 10 to 90% by weight.
(3) The content of other α-olefins having 2 to 8 carbon atoms including ethylene [Y; wt%] and the room temperature xylene soluble content [CXS; wt%] have the following relationship: thing.
0 ≦ 5Y−25 <CXS
[0010]
Here, as the other α-olefin having 2 to 8 carbon atoms in the condition (1), for example, ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, Examples include 1-hexene and 1-octene. Among these, the propylene-based polymer in the present invention is preferably composed of propylene and ethylene.
[0011]
The propylene-based polymer in the present invention has a propylene content of 85 to 95% by weight and another α-olefin content of 2 to 8 carbon atoms including ethylene in the condition (1) of 15 to 5% by weight. %, It is preferable that the content of propylene is 87 to 95% by weight, the content of other α-olefins is 13 to 5% by weight, and the content of propylene is 88 to 92% by weight. The content of other α-olefins is particularly preferably 12 to 8% by weight. When the content of propylene is less than the above range and the content of other α-olefins exceeds the above range, the heat resistance is inferior as a heat sealing material for easily openable containers, while the content of propylene exceeds the above range. If the content of the other α-olefin is less than the above range, the unsealing property is poor as a heat-sealing material for easily-openable containers.
[0012]
Furthermore, in the propylene-based polymer in the present invention, it is essential that the content of the room-temperature xylene-soluble component is 10 to 60% by weight, and preferably 30 to 60% by weight in the condition (2). If the room temperature xylene-soluble content is less than the above range, the openability is poor as a heat-sealing material for easily openable containers, whereas if it exceeds the above range, it is heat resistant as a heat-sealing material for easily openable containers. Will be inferior.
[0013]
Furthermore, the propylene-based polymer in the present invention contains, in the condition (3), the content [Y; wt%] of other α-olefins having 2 to 8 carbon atoms including ethylene and the content of room temperature xylene-soluble matter. It is essential that the quantity [CXS;% by weight] has the relationship of the following formula, and when it does not have the relationship of the following formula, the sealing property and the opening property as a heat sealing material for an easily openable container: The balance will be inferior.
0 ≦ 5Y−25 <CXS
[0014]
The propylene polymer satisfying the above conditions (1) to (3) has a melt flow rate of 0.1 to 50 g / 10 min measured at a temperature of 230 ° C. and a load of 21.18 N in accordance with JIS K7210. The melting point measured by a differential scanning calorimeter at 10 ° C./min in accordance with JIS K7121 is preferably 160 to 170 ° C. Moreover, it is preferable that the bending elastic modulus measured according to JIS K7203 is 150 to 600 MPa, and the tensile strength at break measured according to JIS K7113 is 30 MPa or more.
[0015]
The method for producing the propylene polymer in the present invention is not particularly limited as long as the conditions (1) to (3) are satisfied. Specifically, for example, propylene is homopolymerized in the first stage. After that, in the second step, a sequential polymerization method in which propylene and ethylene, or another α-olefin having 4 to 8 carbon atoms are copolymerized, or propylene and ethylene, or another α having 4 to 8 carbon atoms, is used. -One-stage polymerization method of copolymerizing with olefin.
[0016]
Among these production methods, the propylene-based polymer in the present invention is preferably a sequential polymerization method. The sequential polymerization method will be described in more detail. The catalyst used in this sequential polymerization is an organoaluminum compound, What consists of a titanium atom, a magnesium atom, a halogen atom, and the solid component which essentially requires an electron-donating compound is suitable.
[0017]
Here, as the organoaluminum compound, a general formula R known in this type of polymerization is used.1 mAlX3-m(Wherein R1Represents a hydrocarbon residue having 1 to 12 carbon atoms, X represents a halogen atom, and m is a number of 1 to 3. ), For example, trialkylaluminum such as trimethylaluminum and triethylaluminum, dialkylaluminum halide such as dimethylaluminum chloride and diethylaluminum chloride, alkylaluminum sesquichloride such as methylaluminum sesquichloride and ethylaluminum sesquichloride, methyl Examples thereof include alkylaluminum dihalides such as aluminum dichloride and ethylaluminum dichloride, and alkylaluminum hydrides such as diethylaluminum hydride.
[0018]
In addition, as a solid component essential to a titanium atom, a magnesium atom, a halogen atom, and an electron-donating compound, it is also known in this type of polymerization, and a titanium compound serving as a titanium atom supply source has a general formula Ti (OR2)4-nXn(Wherein R2Represents a hydrocarbon residue having 1 to 10 carbon atoms, X represents a halogen atom, and n is a number of 0 to 4. Among them, titanium tetrachloride, tetraethoxytitanium, tetrabutoxytitanium and the like are preferable. Examples of the magnesium compound serving as a magnesium atom supply source include dialkylmagnesium, magnesium dihalide, and di Alkoxymagnesium, alkoxymagnesium halides and the like can be mentioned, among which magnesium dihalide is preferred. Examples of the halogen atom include fluorine, chlorine, bromine, and iodine. Among them, chlorine is preferable, and these are usually supplied from the titanium compound or the magnesium compound. Or other halogen sources such as tungsten halides.
[0019]
Examples of the electron donating compound include oxygen-containing compounds such as alcohols, phenols, ketones, aldehydes, carboxylic acids, organic acids or inorganic acids and derivatives thereof, and nitrogen-containing compounds such as ammonia, amines, nitriles, and isocyanates. Among them, inorganic acid esters, organic acid esters, organic acid halides, and the like are preferable, silicic acid esters, phthalic acid esters, acetic acid cellosolve esters, phthalic acid halides, and the like are more preferable.ThreeRFour 3-pSi (ORFive)p(Wherein RThreeRepresents a branched aliphatic hydrocarbon residue having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, or a cyclic aliphatic hydrocarbon residue having 5 to 20 carbon atoms, preferably 6 to 10 carbon atoms, and RFourRepresents a branched or straight-chain aliphatic hydrocarbon residue having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and RFiveRepresents an aliphatic hydrocarbon residue having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, and p is a number of 1 to 3. ), For example, t-butyl-methyl-dimethoxysilane, t-butyl-methyl-diethoxysilane, cyclohexyl-methyl-dimethoxysilane, cyclohexyl-methyl-diethoxysilane and the like are particularly preferable.
[0020]
In the sequential polymerization method of the propylene-based polymer in the present invention, propylene is supplied in the first stage, and the temperature is 50 to 150 ° C., preferably 50 to 100 ° C., and the partial pressure of propylene is 0.5 in the presence of the catalyst. -4.5 MPa, preferably 1.0-3.5 MPa, homopolymerization of propylene, followed by propylene and ethylene or propylene and ethylene and carbon atoms of 4 to 8 in the second stage An α-olefin is supplied, and the temperature is 50 to 150 ° C., preferably 50 to 100 ° C. in the presence of the catalyst, and the partial pressures of propylene and ethylene are each 0.3 to 4.5 MPa, preferably 0.5 to 3. It is made by carrying out copolymerization of propylene and ethylene or copolymerization of propylene, ethylene and another α-olefin under the condition of 5 MPa.
[0021]
The polymerization at that time may be any of batch, continuous, and semi-batch, and is preferably carried out in the first stage and second stage of polymerization, in the gas phase or in the liquid phase. It is particularly preferred to carry out the polymerization in the gas phase. The residence time in each stage is 0.5 to 10 hours, preferably 1 to 5 hours.
[0022]
In addition, in order to eliminate the stickiness and the like and impart fluidity to the powder particles of the propylene-based polymer produced by the above-described method, after the polymerization of the component (i) in the first step, (ii ) Before or during the polymerization of the component, the active hydrogen-containing compound is used in an amount of 100 to 1000 times mol of the titanium atom in the solid component of the catalyst and 2 to 5 times mol of the organoaluminum compound of the catalyst. It is preferable to add in the range. Here, examples of the active hydrogen-containing compound include water, alcohols, phenols, aldehydes, carboxylic acids, acid amides, ammonia, amines, and the like.
[0023]
The propylene-based polymer in the present invention has excellent flexibility, transparency and heat resistance equivalent to that of the propylene homopolymer, and excellent mechanical properties such as tensile strength and impact resistance. As a propylene copolymer, it is known by Unexamined-Japanese-Patent No. 2001-226435 etc., for example.
[0024]
Examples of the vinyl monomer in the modified propylene polymer constituting the heat-sealing material for easily openable containers of the present invention include, for example, styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, Aromatic vinyl compounds such as 4-methylstyrene, dimethylstyrene and chlorostyrene, vinyl esters such as vinyl acetate and vinyl propionate, (meth) acrylic acid [where “(meth) acrylic” means “acrylic” "And / or" methacryl ". ], Methyl (meth) acrylate, ethyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) Others such as (meth) acrylic acid or esters thereof such as acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, glycidyl (meth) acrylate, maleic anhydride, dimethyl maleate, di (2-ethylhexyl) maleate Unsaturated carboxylic acids or esters thereof, unsaturated nitriles such as (meth) acrylonitrile, unsaturated mono- or dihalides such as vinyl chloride and vinylidene chloride, and the like. Among them, aromatic vinyl compounds are preferred. , Styrene, 2-methylstyrene It is particularly preferred, especially, styrene is preferred. In the present invention, two or more of these vinyl monomers may be used in combination.
[0025]
In the present invention, the modified propylene polymer is 30 to 95% by weight of the propylene polymer, preferably 40 to 70% by weight, particularly preferably 45 to 65% by weight, and the vinyl monomer 70 to 5% by weight. %, Preferably 60 to 30% by weight, particularly preferably 55 to 35% by weight, obtained by subjecting to graft reaction conditions. If the vinyl monomer is less than this range, the sealing force as a heat sealing material Is too strong, making it difficult to open as an easily openable container. On the other hand, if this range is exceeded, the homogeneity is impaired and cannot be put to practical use.
[0026]
In the present invention, as the graft reaction conditions, basically known methods such as irradiation with an electron beam or addition of a radical generator under melt kneading, in solution or in an aqueous suspension can be adopted. In the present invention, it is preferable to use an aqueous suspension method with addition of a radical generator.
[0027]
The aqueous suspension method with the addition of a radical generator will be specifically described. As the radical generator, a decomposition temperature is preferably 50 ° C. or higher, particularly preferably 50 to 130 ° C., and is oil-soluble. preferable. When the decomposition temperature is less than 50 ° C., the polymerization of the vinyl monomer proceeds abnormally, and it tends to be difficult to obtain a homogeneous modified polymer. Here, the decomposition temperature is the temperature at which 50% of the radical generator decomposes when 0.1 mol of the radical generator is added to 1 liter of benzene and left for 10 hours, so-called “10 hours”. Half-life temperature ".
[0028]
In the present invention, examples of the radical generator include 2,4-dichlorobenzoyl peroxide (decomposition temperature 53 ° C.), t-butyl peroxypivalate (decomposition temperature 55 ° C.), 3,5,5-trimethylhexa Noyl peroxide (decomposition temperature 59.5 ° C), octanoyl peroxide (decomposition temperature 62 ° C), t-butylperoxy-2-ethylhexanoate (decomposition temperature 72.5 ° C), o-methylbenzoyl peroxide (Decomposition temperature 73 ° C), benzoyl peroxide (decomposition temperature 74 ° C), cyclohexanone peroxide (decomposition temperature 97 ° C), 2,5-dimethyl-2,5-di (benzoylperoxy) hexane (decomposition temperature 100 ° C) , T-butylperoxybenzoate (decomposition temperature 104 ° C.), di-t-butyl-diperoxyphthalate Organic peroxides such as dilute peroxide (decomposition temperature 109 ° C.), methyl ethyl ketone peroxide (decomposition temperature 109 ° C.), dicumyl peroxide (decomposition temperature 117 ° C.), di-t-butyl peroxide (decomposition temperature 124 ° C.), Examples thereof include azo compounds such as azobis (2,4-dimethylvaleronitrile) (decomposition temperature 52 ° C.) and azobisisobutyronitrile (decomposition temperature 79 ° C.). In the present invention, two or more of these radical generators may be used in combination.
[0029]
The addition amount of the radical generator is about 0.01 to 10 parts by weight with respect to 100 parts by weight of the vinyl monomer used. If the amount is less than this range, the reaction does not proceed smoothly and is more than this range. And gel tends to occur in the modified polymer.
[0030]
A preferable aqueous suspension graft reaction condition in the present invention is that an aqueous suspension containing a predetermined amount of the propylene polymer, the vinyl monomer, and the radical generator is substantially decomposed by radical generator. In this method, the temperature was raised to a temperature that does not occur in the resin and the propylene polymer was impregnated with the vinyl monomer, and then the temperature was further raised to complete the graft reaction.
[0031]
Here, the aqueous suspension is prepared by adding a vinyl monomer in which a radical generator is dissolved to an aqueous suspension of a propylene-based polymer and stirring, or stirring the vinyl monomer in which a radical generator is dissolved. It is preferable to prepare by any method in which a propylene-based polymer is added to an aqueous suspension and stirred.
[0032]
Further, the content of the propylene polymer and the vinyl monomer in the aqueous suspension is about 5 to 100 parts by weight with respect to 100 parts by weight of water, and in order to maintain a stable dispersion state, for example, Water-soluble polymers such as polyvinyl alcohol, methyl cellulose and hydroxy cellulose, anionic surfactants such as alkylbenzene sulfonate, nonionic surfactants such as polyoxyethylene alkyl ether, or water-insoluble such as magnesium oxide and calcium phosphate It is preferable to use about 0.01 to 10 parts by weight of a suspension stabilizer such as an inorganic salt alone or in combination with respect to 100 parts by weight of water.
[0033]
The impregnation of the vinyl monomer into the propylene polymer is generally performed at room temperature to 100 ° C., preferably 70 to 100 ° C. with stirring, and the free vinyl monomer is 20% by weight of the total amount of the vinyl monomer. Hereinafter, it is preferably performed in about 2 to 8 hours until it becomes preferably 5% by weight or less. Since the propylene polymer is relatively compatible with the vinyl monomer, even if this level of vinyl monomer is liberated before the start of the reaction, these vinyl monomers are not removed during the reaction. To obtain a homogeneous modified polymer.
[0034]
The grafting reaction is generally performed with stirring at a temperature of about 50 to 150 ° C. and a pressure of normal pressure to about 1 MPa for about 2 to 10 hours, and the temperature and pressure during that time must be constant. There is no. In addition, although the propylene-type polymer used for reaction is used with a granular form, it is preferable that it is a particulate form with an average particle diameter of 1-8 mm, especially 3-7 mm.
[0035]
In the present invention, as the modified propylene polymer, the vinyl monomer polymer is 0.2 in the propylene polymer matrix from the viewpoint of sealing power as a heat sealing material and easy opening. It is preferable to have a dispersion structure in which particles are dispersed with a particle diameter of ˜3 μm and a propylene polymer in which the vinyl monomer is graft-polymerized exists at the interface.
[0036]
The easy-open container material of the present invention containing the above-mentioned modified propylene-based polymer is further an olefin polymer other than the modified propylene-based polymer, for the purpose of improving the easy-openability, etc. /as well as,Other than the modified propylene polymerA polymer of vinyl monomers may be contained.
[0037]
Here, as the olefin polymer, for example, homopolymers of α-olefins having about 2 to 8 carbon atoms such as ethylene, propylene, 1-butene, etc., those α-olefins, ethylene, propylene, 1-butene Butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1- Copolymers with other α-olefins having about 2 to 18 carbon atoms such as octene, 1-decene, 1-octadecene, vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, etc. Specifically, for example, ethylene homopolymers such as branched low-density polyethylene and linear high-density polyethylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, Linear low / medium / thylene / propylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, etc. High density ethylene-α-olefin copolymers, ethylene-based resins such as ethylene-vinyl acetate copolymers, ethylene- (meth) acrylic acid copolymers, ethylene- (meth) ethyl acrylate copolymers, propylene Propylene resins such as homopolymers, propylene-ethylene copolymers, propylene-ethylene-1-butene copolymers, and 1-butene homopolymers, 1-butene-ethylene copolymers, 1-butene-propylene Examples thereof include 1-butene resins such as copolymers. Of these, branched low density polyethylene is particularly preferred. In the present invention, two or more of these olefin polymers may be used in combination.
[0038]
Examples of the polymer of the vinyl monomer include polymers and copolymers of vinyl monomers similar to the vinyl monomers listed in the modified propylene polymer. Particularly preferred.
[0039]
In the present invention, the modified propylene-based polymerExceptThe content of these olefinic polymers and / or vinyl monomer polymers contained in the polymer is 800 parts by weight or less as a total amount of both with respect to 100 parts by weight of the modified propylene polymer. Is preferably 1 to 600 parts by weight.
[0040]
The modified propylene polymer, or the olefin polymer other than the modified propylene polymer, and / or theOther than modified propylene polymerIn the heat-sealing material for an easily openable container of the present invention containing a vinyl monomer polymer, a graft and homopolymer of the vinyl monomer produced during the modification of the propylene polymer, and further containing The total content of the vinyl monomer polymer is preferably 5 to 70% by weight, more preferably 6 to 60% by weight, and particularly preferably 7 to 50% by weight. . If the total content of the vinyl monomer polymer is less than this range, the sealing force tends to be too strong as a heat sealing material, and opening tends to be difficult. I don't get it.
[0041]
Incidentally, the heat-sealing material for easily openable containers of the present invention includes the modified propylene polymer,Other than modified propylene polymerOlefin polymer or / and saidOther than modified propylene polymerIn addition to the vinyl monomer polymer, other thermoplastic resins and rubbers, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, and antiblocking agents, as long as the effects of the present invention are not impaired. Agents, lubricants, plasticizers, additives such as pigments, fillers and the like may be blended. These formulations are added in advance to the propylene polymer to be used for modification,Other than modified propylene polymerOlefin polymers andOther than modified propylene polymerIn addition to being added to the vinyl monomer polymer or at the time of preparing the heat sealing material, at the time of production of the modified propylene polymer, for example, by adding it to the vinyl monomer together with a radical generator, etc. Good.
[0042]
The heat-sealing material for easily openable containers of the present invention is the modified propylene polymer, the olefin polymer used as necessary, and / orUsed as neededA polymer of vinyl monomer, and other thermoplastic resins, rubbers, additives and the like are uniformly mixed by a tumbler blender, ribbon blender, V-type blender, Henschel mixer, etc., and then a single or twin screw extruder. It is prepared by melt-kneading with a roll, Banbury mixer, kneader, Brabender or the like.
[0043]
The heat-sealing material for an easily openable container of the present invention is a single layer of the heat-sealing material and may be used for a container lid or a container body as an easily openable container. Resin, polyester resin, saponified ethylene-vinyl acetate copolymer, polycarbonate resin, polystyrene resin, acrylic resin, polyolefin resin, and other thermoplastic resin films, aluminum foil, paper As a lamination method, conventionally known methods such as a glue lamination method, an extrusion lamination method, and a co-extrusion method with the above-mentioned various thermoplastic resins are adopted. In addition, it is preferable that the thickness of the heat sealing material layer of this invention in that case shall be about 5-100 micrometers.
[0044]
The easy-open container of the present invention has a heat-sealing structure in which the heat-sealing material for easy-open containers and the surface of the adherend are heat-sealed. The adherend is not particularly limited, but is preferably a propylene resin, and the propylene resin is the same as the olefin polymer other than the modified propylene polymer. A propylene-based resin may be used, and the propylene-based resin may be either a single layer or a laminated state as long as it forms a surface.
[0045]
In the present invention, a specific form of an easily openable container is as follows. For example, (1) a packaging container composed of a container body and a lid material, A heat-sealing material for a conductive container is used on the lid side, and includes a container body having a propylene-based resin on the heat-sealing surface and a lid material having the heat-sealing material on the heat-sealing surface. An easily openable container, (b) the case where the heat sealant for an easily openable container of the present invention is used on the container body side, a container body having the heat sealant on the heat sealing surface, and a propylene-based material (2) As a packaging bag, (a) the case where the heat-sealing material for an easily-openable container of the present invention is used on both sides of the bag. An easily openable container, which is a bag body heat-sealed by facing the heat-sealing materials of the bag member having the heat-sealing material on the heat-sealing surface, and b) The case where the heat sealing material for easily openable containers of the present invention is used on one side of a bag and a bag member having a propylene-based resin on the heat sealing surface is used on the other side. An easily openable container which is a bag body in which a bag member having a dressing material on a heat sealing surface and a propylene resin surface of a bag member having a propylene resin on a heat sealing surface is heat sealed.
[0046]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. The modified propylene polymer used in the examples is shown below.
[0047]
[Production of modified propylene polymer]
<Production of solid component catalyst>
20 liters of dehydrated and deoxygenated n-heptane was introduced into a tank equipped with a stirrer with an internal volume of 50 liters purged with nitrogen, and then 4 moles of magnesium chloride and 8 moles of tetrabutoxytitanium were introduced and reacted at 95 ° C. for 2 hours. After that, the temperature was lowered to 40 ° C., 480 ml of methylhydropolysiloxane (viscosity 20 centistokes) was introduced, and the mixture was further reacted for 3 hours. Then, the reaction solution was taken out and the produced solid component was washed with n-heptane. . Next, 15 liters of dehydrated and deoxygenated n-heptane was introduced into the tank using the stirrer tank, and then 3 mol of the obtained solid component was introduced in terms of magnesium atom, and further 8 mol of silicon tetrachloride. Was added to 25 ml of n-heptane over 30 minutes at 30 ° C., the temperature was raised to 90 ° C. and reacted for 1 hour, the reaction solution was taken out, and the resulting solid component was n-heptane. Washed with. Subsequently, 5 liters of dehydrated and deoxygenated n-heptane was introduced into the tank using the tank with a stirrer, and then 250 g of the titanium-containing solid component obtained above, 750 g of 1,5-hexadiene, t- After introducing 130 ml of butyl-methyl-dimethoxysilane, 10 ml of divinyldimethylsilane, and 225 g of triethylaluminum respectively and contacting them at 30 ° C. for 2 hours, the reaction solution is taken out and washed with n-heptane to obtain a solid component catalyst. Obtained. The obtained solid component catalyst had a prepolymerization amount of 1,5-hexadiene of 2.97 g per titanium-containing solid component.
[0048]
<Production of propylene polymer>
In a first-stage reactor having an internal volume of 550 liters, an amount ratio of propylene, triethylaluminum, and a polymer production rate of 20 kg / hour is set to a pressure of about 3.2 MPa at a temperature of 70 ° C. Polymerization was carried out in the liquid phase by continuously supplying the solid component catalyst and further supplying hydrogen as a molecular weight control agent (first stage polymerization). Subsequently, the produced polymer is introduced into a second-stage reactor having an internal volume of 1900 liters through a propylene purge tank, and the produced copolymer has a temperature of 60 ° C. and a pressure of 3.0 MPa. A solid component catalyst in which propylene and ethylene are continuously supplied according to the composition ratio of hydrogen, and hydrogen as a molecular weight control agent is continuously supplied, and an active hydrogen compound (ethanol) is supplied in the first stage. After supplying 200 moles of titanium atoms and 2.5 moles of triethylaluminum to conduct polymerization in the gas phase, the resulting polymer was continuously transferred to a vessel. Then, nitrogen gas containing moisture was introduced to stop the reaction (second stage polymerization). Thus, a propylene-ethylene copolymer (A) as a propylene polymer was produced.
[0049]
The obtained propylene-ethylene copolymer (A) had an ethylene content (Y) of 10.2% by weight and a room temperature xylene-soluble content (CXS) measured by the following method. It was 7% by weight, and “5Y-25” was 26. The melt flow rate was 8 g / 10 min, the melting point was 164.2 ° C., the flexural modulus was 318 MPa, and the tensile strength at break was 36 MPa.
[0050]
<Content of ethylene (Y)>
Measured by infrared spectroscopy.
<Room-temperature xylene-soluble content (CXS)>
1 g of a sample was dissolved in 300 ml of xylene with stirring at a boiling point of xylene of 140 ° C. After 1 hour, the temperature was lowered to 100 ° C. within 1 hour while continuing stirring, and then transferred to a quenching oil bath and stirred. While continuing to cool rapidly to 23 ± 2 ° C., the polymer was precipitated and allowed to stand for 20 minutes or longer, then the precipitate was naturally filtered with filter paper, the filtrate was evaporated to dryness with an evaporator, and further dried at 120 ° C. under reduced pressure for 2 hours. The mixture was allowed to cool to room temperature and the weight was measured.
[0051]
<Melt flow rate>
According to JIS K7210, the measurement was performed at a temperature of 230 ° C. and a load of 21.18 N.
<Melting point>
Using a differential scanning calorimeter (manufactured by Seiko Instruments Inc.), the melting peak temperature was measured at a heating rate of 10 ° C./min in accordance with JIS K7121.
<Bending elastic modulus>
It measured at 23 degreeC based on JISK7203.
<Tensile breaking strength>
In accordance with JIS K7113, measurement was performed at 23 ° C. and a tensile speed of 50 mm / min using a No. 2 dumbbell.
[0052]
<Manufacture of modified propylene polymer>
In an autoclave with a capacity of 50 liters, 20 kg of water, 0.6 g of sodium dodecylbenzenesulfonate as a suspending agent, and 0.6 kg of tribasic calcium phosphate as a suspending aid are added to form an aqueous medium. 6 kg of particles having an average particle diameter of 3 to 4 mm of the obtained propylene-ethylene copolymer (A) were added and stirred to obtain an aqueous suspension. To this aqueous suspension, 6 kg of a styrene monomer in which 15.6 g of 3,5,5-trimethylhexanoyl peroxide and 9 g of benzoyl peroxide were dissolved as a radical generator was added, and nitrogen was introduced into the autoclave. 0.5kg / cm2Then, the temperature inside the autoclave was raised to 55 ° C. and stirred at this temperature for 6 hours to impregnate the propylene polymer particles with the entire amount of the styrene monomer containing the radical generator. Subsequently, the temperature inside the autoclave was raised to 100 ° C. and stirred at this temperature for 3 hours to carry out the grafting reaction. The temperature was further raised to 120 ° C. and stirred at this temperature for 15 hours to complete the reaction. After cooling, the reaction solid was taken out and washed with water to obtain 12 kg of particulate modified propylene-ethylene copolymer (A ′) particles. The obtained modified propylene-ethylene copolymer (A ′) contained 50% by weight of polystyrene.
[0053]
Examples 1-3
The pellets of the modified propylene-ethylene copolymer (A ′) obtained above or, alternatively, with respect to 100 parts by weight of the modified propylene-ethylene copolymer, low density polyethylene (density 0.913 g / cmThree, 190 ° C., melt flow rate measured at a load of 21.18 N 7 g / 10 min), or polystyrene (density 1.1 g / cm)Three, 200 ° C., melt flow rate 6 g / 10 min measured at a load of 49.03 N) is added in the amount shown in Table 1, they are supplied to a single screw extruder and melt-kneaded at 210 ° C. to be pelletized. The pellets were supplied to a 35 mm diameter film molding machine (Placo) equipped with a T-die, melt extruded at 230 ° C., and cooled to form a 30 μm thick film. A two-layer laminated film was prepared by adhering to a polyethylene terephthalate film having a thickness of 20 μm using an agent.
[0054]
On the other hand, on the flange portion of a rectangular container body produced by thermoforming from a sheet of polypropylene resin having a thickness of 200 μm, the laminated film is used as a cover material, and the modified propylene-ethylene copolymer layer is used as an adhesive surface. An easy-open container was prepared by heat sealing under the conditions shown below, and the peel strength of each of the obtained containers was measured by the method shown below. The results are shown in Table 1.
[0055]
<Peel strength>
Using a hot plate heat sealer, temperature 160 ° C, 170 ° C, 180 ° C, or 190 ° C, pressure 1.96 x 10FivePa, time 0.5 seconds, the cover material was thermocompression bonded to the container body flange portion with a width of 5 mm, the bonded portion was sampled with a length of 15 mm, and an Instron type tensile tester was used to make a perpendicular to the length. The peel strength at 180 degrees (g / 15 mm) was measured by peeling at 23 ° C. and a tensile speed of 300 mm / min.
[0056]
Furthermore, for each easily openable container obtained above, the heat resistance of the heat sealing part was evaluated by the method shown below, and the results are shown in Table 1.
<Heat resistance of heat seal part>
The easy-open container was placed in an oven adjusted to 135 ° C. for 30 minutes, then removed, and the appearance of the heat-sealed portion was visually observed and evaluated according to the following criteria.
○: No sag, wrinkle, float, or peeling on the heat-sealed part.
X: Sagging, wrinkling, floating, or peeling is observed in the heat sealing part.
[0057]
Comparative Example 1
Instead of the propylene-ethylene copolymer (A), the ethylene content is 4% by weight, the room temperature xylene soluble content is 0% by weight, the melt flow rate is 5 g / 10 min, and the melting point is 145.1 ° C. Example 1 except that a modified propylene-ethylene copolymer (B ′) obtained by modifying a propylene-ethylene copolymer (B ′) having a flexural modulus of 700 MPa and a tensile breaking strength of 35 MPa was used. It was.
[0058]
Comparative Example 2
Instead of the propylene-ethylene copolymer (A), the room temperature xylene soluble content is 0% by weight, the melt flow rate is 8 g / 10 min, the melting point is 164.3 ° C., the flexural modulus is 1,300 MPa, Example 1 was the same as Example 1 except that a modified propylene homopolymer (C ′) obtained by modifying a propylene homopolymer (C) having a tensile strength at break of 40 MPa was used.
[0059]
[Table 1]
From Table 1, in Comparative Examples 1 and 2, the difference in peel strength between the heat sealing temperature of 160 ° C. and 190 ° C. is as large as 2,500 to 3,500 g / 15 mm. While the strength is not stable and the balance between the sealing property and the opening property is inferior, in Examples 1 to 3, the difference is as small as 800 to 1,100 g / 15 mm, even by the difference in the heat sealing temperature, It is clear that stable peel strength is exhibited, the balance between sealing property and opening property is excellent, and heat resistance is also excellent.
[0061]
【The invention's effect】
According to the present invention, it is possible to form a heat sealing portion that has a sufficient sealing force, is easy to open at the time of opening, and also has heat resistance, and in particular has a propylene-based resin on the heat sealing surface. It is possible to provide a heat-sealing material for easily openable containers suitably used for a packaging container or a packaging bag and an easily openable container using the same.
Claims (8)
（１）プロピレンの含有量が８５〜９５重量％、エチレンを含む炭素数２〜８の他のα−オレフィンの含有量が１５〜５重量％であること〔ここで、「重量％」は、プロピレンと、エチレンを含む炭素数２〜８の他のα−オレフィンとの合計量に対するものである。〕。
（２）室温キシレン可溶分の含有量が１０〜９０重量％であること。
（３）エチレンを含む炭素数２〜８の他のα−オレフィンの含有量〔Ｙ；重量％〕と室温キシレン可溶分の含有量〔ＣＸＳ；重量％〕とが、下式の関係を有すること。
０≦５Ｙ−２５＜ＣＸＳModification obtained by subjecting 30 to 95% by weight of a propylene polymer satisfying the following conditions (1), (2) and (3) and 70 to 5% by weight of a vinyl monomer to graft reaction conditions A heat-sealing material for easily openable containers, comprising a propylene-based polymer.
(1) The content of propylene is 85 to 95% by weight, and the content of other α-olefins having 2 to 8 carbon atoms including ethylene is 15 to 5% by weight [where “% by weight” It is based on the total amount of propylene and other α-olefins having 2 to 8 carbon atoms including ethylene. ].
(2) The content of room temperature xylene solubles is 10 to 90% by weight.
(3) The content of other α-olefins having 2 to 8 carbon atoms including ethylene [Y; wt%] and the room temperature xylene soluble content [CXS; wt%] have the following relationship: thing.
0 ≦ 5Y−25 <CXS
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