JP4036348B2

JP4036348B2 - Vinylidene chloride resin thin film molded article and method for producing the same

Info

Publication number: JP4036348B2
Application number: JP27578697A
Authority: JP
Inventors: 卓中尾; 智志橋本; 偉入矢
Original assignee: Asahi Kasei Chemicals Corp
Current assignee: Asahi Kasei Chemicals Corp
Priority date: 1997-10-08
Filing date: 1997-10-08
Publication date: 2008-01-23
Anticipated expiration: 2017-10-08
Also published as: JPH11106525A

Description

【０００１】
【発明の属する技術分野】
本発明は、食品、医薬品包装材料等に使用される酸素遮断性、防湿性等に優れたフィルム、シート容器等に利用される薄膜成形物に関する。より詳細には、色調の改良された、塩化ビニリデンと塩化ビニルとの共重合体からなる樹脂薄膜成形物に関する。
【０００２】
【従来の技術】
塩化ビニリデン系樹脂は、その優れた酸素遮断性、防湿性から包装材用途に広く使用されている。また、塩化ビニリデン系樹脂薄膜成形体の直接押出成形には、特表平４−５０１５８０号公報に、「塩化ビニリデン共重合体（コポリマー）の押出加工は、単軸もしくは多軸スクリュー押出機を用いて行われ、特に塩化ビニリデンコポリマーのように熱に敏感なコポリマーには単軸スクリュー押出機がしばしば用いられる。」との記載があるように、通常、単軸スクリュー押出機が公知技術として用いられている。なお、特表平３−５０４０２３号公報にはポリ塩化ビニリデン共重合体を含むポリマー組成物からなる感熱性ポリマーを溶融加工する装置として、加熱二本ロール配合機、ブラベンダーミキサー、バンバリーミキサー、単軸押出機、二軸押出機等を用いることが記載されており、実施例にはパウダー混合物を、ＬｅｉｓｔｒｉｔｚＭｏｄｅｌＮｏ．ＬＳＭ−３０．４０なる３４ｍｍ二軸配合押出機で押出すことが記載されている。この押出機は小型実験用マルチ押出機であり、その二本のスクリュー回転方向が異方向回転、同方向回転の何れにも組み替え可能な機種であるが、該公報にはその詳細は記述されておらず、一般的には異方向回転型に分類されるものである。また、この異方向回転二軸押出機はポリ塩化ビニル系樹脂では、通常よく使用される形式のものであるが、該公報ではペレタイズ用途に用いられており、薄膜成形物を押出機から直接成形するものではない。事実、前記公報の実施例においてはペレット化後のテープ状の押出物の成形にはスクリュー口径２．５インチの単軸押出機が用いられると記載されている。
【０００３】
しかしながら、塩化ビニリデン系樹脂は、一般のポリエチレン等の熱可塑性樹脂と比較して溶融加工時に熱劣化がしやすいという欠点があり、かかる欠点のために、成形加工の際の色調変化（成形物の着色）や、成形条件の許容範囲が狭い等の問題が生じており、特に、成形物の着色は透明性を要求される用途においては深刻な問題となっていた。更に、塩化ビニリデン系樹脂薄膜成形物の成形においては、粉体状の原料を押出加工するため、単軸押出機を用いた場合に、固体搬送部での搬送斑が発生しやすく、薄膜成形物を巻き取る際にシワが発生したり、得られた薄膜成形物において弾性差が生じ、取扱い性に劣る等の問題も生じていた。
【０００４】
かかる塩化ビニリデン系樹脂の成形時の熱安定性を改善するために、従来より特公昭６２−５７６６３号公報等に記載されるように、各種添加剤の検討がなされてきたが、熱劣化による色調変化を抑制し、かつ、極微量の添加により、その効果が発現する添加剤は未だ見いだされておらず、各種添加剤の量を増加させることで対応してきた。しかしながら、添加剤の量を増加させることは、塩化ビニリデン樹脂の本来の特性である酸素遮断性を低下させることになり、また薄膜状の成形物の場合には、多量の添加により薄膜表面に添加剤がブリードアウトして、薄膜表面のべとつき・粉ふき等の問題を生じることになる。従って、添加剤による熱劣化の改善には自ずとその限界があった。
【０００５】
また、塩化ビニリデン系樹脂成形物の樹脂構造に対する検討を行ったものとして、特開平９−７７８２７号公報がある。この公報には結晶化度が高い成形物を得るために、塩化ビニリデン系樹脂として、式−（ＣＨ₂−ＣＣｌ₂−ＣＨ＝Ｃｌ−ＣＨ₂−ＣＣｌ₂）−で表される単位を０．００１〜０．０２重量％含有する樹脂を用いることが記載されている。しかしながら、この公報に記載された発明は成形物の結晶化度に着目したものであり、溶融加工時の熱劣化の改善を目的としたものではない。また、従来法と同様に単軸押出機を用いて成形されており、成形物の着色の度合いが十分なものではなかった。
【０００６】
【発明が解決しようとする課題】
本発明の第１の課題は、上記従来技術の欠点を克服し、着色の少ない塩化ビニリデン系樹脂薄膜成形物を提供すること、より詳細には、塩化ビニリデン樹脂本来の特性である酸素遮断性や引張弾性率等の物性を低下させることになく、着色の少ない塩化ビニリデン系樹脂薄膜成形物を提供することである。
本発明の第２の課題は、着色の少ない塩化ビニリデン系樹脂薄膜成形物を安定して供給できる製法を提供することである。
【０００７】
【課題を解決するための手段】
本発明者らは、上記従来技術の欠点を克服し、着色の少ない薄膜成形物を提供するために、塩化ビニリデン系樹脂の熱劣化による色調変化の主要な因子である脱塩酸の挙動について検討を行った。また、その際、本発明者らは、最終的に消費者の手に入る時点で着色の少ない薄膜成形物を提供するためには、成形直後の着色性を改善するだけでなく、経時的な色調変化をも改善することが極めて重要であることに着目した。そして、溶融加工時に脱塩酸し樹脂中に生成した二重結合の共役度合いを制御し、得られる薄膜成形物のＵＶ値及びＮＭＲ値を特定の範囲内のものとすることで、加工後の薄膜成形物の色調変化を抑制できることを見出し、本発明に至った。
【０００８】
即ち、本発明は、以下の（１）および（２）である。
（１）塩化ビニリデン部分７０〜９５重量％、塩化ビニル部分５〜３０重量％からなる共重合体からなり、完全噛合型同方向回転二軸押出機を用いて押出成形する工程を含む製造方法によって製造される塩化ビニリデン系樹脂薄膜成形物であって、ＵＶ値が０．４〜０．９、ＮＭＲ値が０．１×１０ ^-4 〜３．５×１０ ^-4の範囲にあり、かつＵＶ値とＮＭＲ値の関係が、ＵＶ値≦１．６５×１０³×ＮＭＲ値＋０．４５の範囲にあることを特徴とする塩化ビニリデン系樹脂薄膜成形物。
（２）塩化ビニリデン部分７０〜９５重量％、塩化ビニル部分５〜３０重量％からなる共重合体を、完全噛合型同方向回転二軸押出機を用いて溶融加工することを特徴とする請求項１記載の塩化ビニリデン系樹脂薄膜成形物の製造方法。
【０００９】
以下、本発明について詳細に説明する。
本発明でいう薄膜成形物とは厚みが５μｍから２ｍｍの範囲にあるものであり通常、フィルム、シートと呼ばれるものすべてに適用される。その中でも特に、５μｍから３０μｍの厚みのフィルムに好適に適用される。
本発明の成形物を構成する塩化ビニリデン系樹脂とは、塩化ビニリデンモノマーと塩化ビニルモノマーの共重合体樹脂であり、その樹脂部分の組成比は塩化ビニリデン部分が７０〜９５重量％であり、塩化ビニル部分が５〜３０重量％である。塩化ビニリデン部分の含有量が７０重量％未満であると、酸素遮断性および防湿性などの塩化ビニリデンを主成分とした成形物の特徴となる性質を著しく損ない、また９５重量％を越えると共重合体の分解点と成形温度が近くなり、溶融成形性が著しく低下してしまうため、その使用が制限される。その性能と成形性からみると、好ましくは、塩化ビニリデン部分は８０〜９５重量％の範囲である。この共重合体で塩化ビニリデン部分は樹脂中にブロック的に存在し、塩化ビニリデン部分の平均的ブロック数は２以上である。
【００１０】
また、該樹脂の重量平均分子量は５，０００〜５００，０００であることが好ましく、更に好ましくは５０，０００〜１００，０００の範囲である。重量平均分子量が５，０００未満のものでは成形物の機械的強度が低下するため、５００，０００を越えるものでは溶融加工性が低下するためその使用が制限される。また、重量平均分子量と数平均分子量の比は、１．１〜５の範囲にあることが好ましい。この重量平均分子量及び数平均分子量はテトラヒドロフラン（以下ＴＨＦと略す）を溶媒とし、該樹脂を０．０５重量％の濃度で溶解させ、分子量既知の単分散ポリスチレンを標準物質として用いたゲルパーミエーションクロマトグラフ法（東ソー（株）製ＧＰＣ８０００シリーズ使用）により測定した値を採用する。
【００１１】
なお、本発明の塩化ビニリデン系樹脂は既に公知の重合方法を採用することができ、好ましくはいわゆる懸濁重合法により重合されるものである。
また、熱安定剤、可塑剤等の各種添加剤については、所望の性質を変えない範囲でかつ、本発明の範囲内であれば公知のものの中から、適宜選択して使用しうる。そのような添加剤の例としては、アセチルクエン酸トリブチル、セバチン酸ジブチル、ポリエチレングリコール脂肪酸エステル、アセチル化モノグリセリド、エポキシ化アマニ油、エポキシ化大豆油等が挙げられる。添加剤の添加量は、酸素遮断性、防湿性、引張弾性率等の点から、好ましくは、樹脂に対して１〜１２重量％、より好ましくは１〜１０重量％、更には２〜８重量％である。
【００１２】
本発明の成形物は、ＵＶ値が０．４〜０．９、ＮＭＲ値が０．１×１０ ^-4 〜３．５×１０ ^-4の範囲にあり、かつＵＶ値とＮＭＲ値の関係が、ＵＶ値≦１．６５×１０³×ＮＭＲ値＋０．４５の範囲にあることが必須である。
本発明におけるＵＶ値は、次の方法にて求めた値を採用する。まず、樹脂成形物を１．００ｇ採取し、密閉容器中で測定溶媒である分光分析用テトラヒドロフラン（ＴＨＦ）１００ｃｃと混ぜ合わせ、５０℃に保温し１時間、振とう器にて成形物を均一に溶解させる。次に紫外吸収分光用標準石英セル（光路長１０ｍｍ・透過面２面）に該溶解液を入れ、ＴＨＦ溶液単体を測定ブランクセルとして、紫外吸収分光分析用測定装置（島津製作所製「ＵＶ２１００」光源は、重水素ランプ、スキャンニングスピードはミディアム、スリット幅は２．００ｎｍ、測定器雰囲気温度２３℃）にて、５００ｎｍ〜１９０ｎｍまでの範囲の吸光度を測定する。この吸光度のうち、２４０ｎｍにおける吸光度の値をＵＶ値とする。
【００１３】
また、本発明におけるＮＭＲ値は、本発明の成形物を構成する塩化ビニリデン系樹脂の重量を１００としたときの、−（ＣＨ₂−ＣＣｌ₂）−（ＣＨ＝ＣＣｌ）−（ＣＨ₂−ＣＣｌ₂）−連鎖中の−（ＣＨ＝ＣＣｌ）−のプロトンの割合として定義され、次の方法にて求めた値を採用する。まず、樹脂成形物を５０ｍｇ採取し、試料管に入れ、測定溶媒である重水素化ＴＨＦを１ｇ加え、均一に溶解させる。高分解能プロトン核磁気共鳴装置（日本電子株式会社製「α−４００」）にて測定を行う。条件は、測定時間２秒、間隔時間５秒、積算回数１０００回にて行い、テトラメチルシランを基準とした化学シフトを横軸としたスペクトルを得る。このうち、−ＣＨ₂−のプロトンのシグナル領域である２．０〜４．２ｐｐｍのシグナルに着目し、２．４〜２．６ｐｐｍのシグナルを−ＣＨ₂−ＣＣｌ₂−ＣＨ₂−ＣＣｌ₂−のプロトンに、３．０〜３．４ｐｐｍのシグナルを−ＣＨ₂−ＣＣｌ₂−ＣＨ₂−ＣＨＣｌ−のプロトンに、３．７〜４．２ｐｐｍのシグナルを−ＣＨ₂−ＣＨＣｌ−ＣＨ₂−ＣＨＣｌ−のプロトンに帰属させて、これらのシグナルのスペクトル面積値（ＮＭＲスペクトルにおけるピークの面積）から、当該薄膜成形物の樹脂組成比（塩化ビニリデン部分と塩化ビニル部分の比）をまず求める。
【００１４】
次いで、塩化ビニル部分の−ＣＨＣｌ−のプロトンに由来する４．４〜５．２ｐｐｍのシグナルのスペクトル面積値と、−（ＣＨ₂−ＣＣｌ₂）−（ＣＨ＝ＣＣｌ）−（ＣＨ₂−ＣＣｌ₂）−連鎖中の−（ＣＨ＝ＣＣｌ）−のプロトンに由来する７．０１ｐｐｍのシングレットピークのスペクトル面積値とから両者のプロトンの重量比を求める。この重量比と上記樹脂組成比（塩化ビニル部分と塩化ビニリデン部分の比）とから、塩化ビニリデン系樹脂に対する、−（ＣＨ₂−ＣＣｌ₂）−（ＣＨ＝ＣＣｌ）−（ＣＨ₂−ＣＣｌ₂）−連鎖中の−（ＣＨ＝ＣＣｌ）−のプロトンの重量百分率を求める。
【００１５】
一般に塩化ビニル系樹脂及び塩化ビニリデン樹脂及びその薄膜成形物の着色原因は、主に樹脂中に含まれる脱塩酸後の二重結合が、共役系を形成することであるといわれている。したがって、本質的に樹脂の着色を防止するためには、この二重結合の共役系を成長させないことが非常に重要となる。
前述のように、本発明でのＵＶ値は、２４０ｎｍでの吸光度値を採用し、３〜４個程度に共役した二重結合量に対応しており、成形物の着色に強く相関する値である。またＮＭＲ値は、分子鎖中の塩化ビニリデンの三連鎖ブロックの中央の塩化ビニリデン部分から脱塩酸した二重結合量、つまり孤立した二重結合量に対応しているものであり、この値は直接着色に影響を与えない指標である。
【００１６】
本発明の成形物のＵＶ値は０．２〜１．５であり、成形物の着色抑制の点から、好ましくは０．４〜０．９であり、より好ましくは０．４５〜０．８５、さらに好ましくは０．５〜０．８である。ＵＶ値が０．２未満の値は、本発明の範囲では溶融加工に適した添加剤を含む樹脂組成では実質的に発生せず、１．５を超えるものは薄膜成形物の着色度合いが大きくなるために制限される。
【００１７】
本発明の成形物のＮＭＲ値は０．１×１０^-4〜６．４×１０^-4であり、好ましくは０．１×１０^-4〜３．５×１０^-4であり、より好ましくは０．２×１０^-4〜３×１０^-4、さらに好ましくは０．３×１０^-4〜２×１０^-4である。ＮＭＲ値の下限値の０．１×１０^-4は微視的な分子鎖の構造について均一性を確保するために必要な値である。また上限値の３．５×１０^-4を超えるものは共役二重結合の生成に移行しやすく、結果として着色の程度が大きくなるため制限される。
【００１８】
更に、本発明の成形物は、ＵＶ値とＮＭＲ値の関係が、
ＵＶ値≦１．６５×１０³×ＮＭＲ値＋０．４５
であることが必須である。成形物の着色の経時変化の点から、好ましくはＵＶ値≦１．６５×１０³×ＮＭＲ値＋０．４２５、より好ましくはＵＶ値≦１．６５×１０³×ＮＭＲ値＋０．４である。ＵＶ値及びＮＭＲ値がたとえそれぞれ０．２〜１．５及び０．１×１０^-4〜６．４×１０^-4の範囲にあっても上記関係式を満たさない場合には、成形後の色調或いは経時的な色調変化において、十分な成形物を得ることができない。
【００１９】
従来の成形物は孤立二重結合が生成すると、それに対応して共役二重結合も増加し、ＵＶ値とＮＭＲ値とがＵＶ値＞１．６５×１０³×ＮＭＲ値＋０．４５の関係にあり、色調が著しく変化する。これに対して、上記関係式を満たす本発明の成形物は、溶融加工により熱劣化し、生成する二重結合が、相対的に孤立二重結合になりやすく、共役二重結合に進みにくいのではないかと思われる。すなわち、本発明の成形物は上記関係式を満たすことにより、溶融加工時、脱塩酸して生成する二重結合の共役する割合が相対的に低くなり、着色度合いが著しく改善されるものと考えられる。さらに、本発明の成形物では、成形加工直後の色調も良好であることに加えて、成形物のエージング等による経時的な色調変化も少ない。これは、成形直後の成形物に相対的に孤立二重結合が多いことにより、エージング等により経時的に脱塩酸をしたとしても、着色に結びつく長鎖の二重結合共役系を成長させにくいのではないかと考えられる。
【００２０】
本発明における上記範囲を図１に示す。図１において、縦軸は薄膜成形体のＵＶ値を示し、横軸はＮＭＲ値を示す。図１中の斜線の部分が本発明の範囲を示す。
本発明の範囲内のものは、範囲外のものと比較して前述の様に色調の点で良好であり、成形加工後の変色などの色調変化、経時的な色調変化も少ない。また、酸素ガス透過度や引張弾性率などのフィルム物性の点でも、良好な薄膜が得られている他、押出加工時の生産性の点も良好である。これは例えば、通常公知の塩化ビニリデン系樹脂薄膜成形法であるインフレーションバブル法により薄膜を得る際のインフレーションバブルのパンク頻度及び製品品質を損なう熱劣化物の混入等の押出生産性が、本発明の範囲外のものより高くなっている。これについてははっきりした理由は判らないが、微視的な観点で、本発明ののものは分子鎖の均一性が高く、その為か、添加剤の分布を均一にさせ、局所的な熱劣化を抑制する効果があると考えられ、これがバブルのパンク抑制に効果を与えるものと考えている。
【００２１】
本発明の成形物は酸素遮断性等、塩化ビニリデン系樹脂の本来有する特性を維持したまま、色調変化等が改善されている。本発明の成形物は、後述の方法により測定した酸素ガス透過度が１００ｃｃ／（ｍ²・２４ｈｒｓ・ａｔｍ）以下であることが好ましい。
本発明の上記範囲にある薄膜成形体を得るための製造法としては、樹脂組成比が、塩化ビニリデン部分７０〜９５重量％、塩化ビニル部分５〜３０重量％からなる共重合体を、二軸押出機を用いて溶融加工することで達成しうる。ここで、二軸押出機とは、二本の押出スクリューを有する公知の押出機である。
【００２２】
前述の通り、塩化ビニリデン系樹脂薄膜成形物の直接押出成形においては、従来、単軸押出機が用いられてきた。これに対して、本発明では、二軸押出機、更には特定の二軸押出機を特定の条件で用いることにより、上記特性を有する新規な薄膜成形物を安定して供給することに成功したものである。このことは、後述の実施例、比較例をグラフ化した図１からも明らかである。即ち、図１に示す通り、従来の単軸押出機を用いて製造した薄膜成形物は、いずれもＵＶ値とＮＭＲ値の範囲が本発明の範囲外であり、そのため、色調変化において劣る。また、後述の比較例に示す通り、その押出生産性は劣るものである。
【００２３】
本発明における溶融押出加工を行うためには、一般に記載されている二軸押出機を用いてニーディングディスクの選定及びスクリュー回転数等の最適化によりその押出温度を低く抑えることにより可能であるが、特に完全噛合型同方向回転二軸押出機を用いて溶融することにより、本発明の目的である変色の少ない成形物を得ることが可能である。また、好ましくは完全噛合型同方向回転二軸押出機の中で、スクリュー径Ｄに対してスクリュー全長Ｌの比Ｌ／Ｄが１５〜３０の範囲の押出機を用いて、スクリュー構成、押出量、スクリュー回転数、バレル温度を調節して、押出機スクリュー先端部の樹脂温度１７０〜１９０℃、好ましくは１７５〜１８０℃の範囲内で溶融を行う。
【００２４】
二軸押出機を用いることにより、スクリューフライトの山部分で相手のスクリューフライトの谷部分を掻き出す、いわゆる「セルフクリーニング」性を有し、スクリューフライト壁面に付着する長時間滞留物を未然に防ぐ効果が考えられる。また、原料を溶融させる際、二軸押出機ではスクリュー構成を任意に設定できるため、ニーディングディスク部分での溶融を最適条件に制御することが可能である。
【００２５】
本発明の製造方法においては、使用する塩化ビニリデン系樹脂の共重合組成及び平均分子量を、本発明の範囲内で変化させ、押出樹脂温度をより低く抑えることも採用しうる。具体的には、平均分子量の低い塩化ビニリデン系樹脂をブレンドすることで、加工時の溶融粘度を低下させ、押出樹脂温度を下げること等により対応するものである。
【００２６】
また、本発明は、別発明として、塩化ビニリデン部分７０〜９５重量％、塩化ビニル部分５〜３０重量％からなる共重合体からなる塩化ビニリデン系樹脂薄膜成形物であり、厚み斑が±５％未満、好ましくは±４．５％未満、更に好ましくは±４．％未満である厚み５〜３０μｍの塩化ビニリデン系樹脂薄膜成形物をも含む。この場合には、厚み斑が上記範囲にあることにより、薄膜成形物を巻き取る際に、シワ等のない均一な巻物が得られ、また食品等の包装用フィルムにおいては、弾性差が発生しにくいために取扱い性に優れる等の効果を生ずる。そして、かかる薄膜成形物は二軸押出機を用いた上記方法を採用することにより、初めて提供できたものである。
【００２７】
すなわち、二軸押出機では、その固体搬送部での原料粉体が均一に輸送されるために、上記厚み斑が達成できるものと考えられる。上記厚み斑が±５％未満である塩化ビニリデン系樹脂薄膜成形物の好ましいＵＶ値、ＮＭＲ値の範囲は、第１の本発明と同様の理由で、各々、０．２〜１．５（より好ましくは０．４〜０．９であり、更に好ましくは０．４５〜０．８５、最も好ましくは０．５〜０．８）、０．１×１０^-4〜６．４×１０^-4（より好ましくは０．１×１０^-4〜３．５×１０^-4であり、更に好ましくは０．２×１０^-4〜３×１０^-4、最も好ましくは０．３×１０^-4〜２×１０^-4）であり、更に、ＵＶ値とＮＭＲ値の関係が、ＵＶ値≦１．６５×１０³×ＮＭＲ値＋０．４５であることが最も好ましい。なお、好ましい添加剤及びその添加量は上記第１の発明と同様である。
【００２８】
【発明の実施の形態】
次に本発明を実施例および比較例に基づいてより具体的に説明する。
成形物の評価は下記に示す方法で行った。
（１）成形物の着色
「プラスチックの光学的特性試験方法」（ＪＩＳＫ７１０５）に従って、本発明の共重合体成形物の色について測定する。実施例及び比較例での測定法を以下に示す。日本電色工業株式会社製Ｚ−ＩＩ型を測定装置として使用する。押出した円筒状の成形物の円筒部分を潰し平たいシート状とし測定用試料を採取する。これの標準白色面からの反射光の色差ｂ値を測定する。測定は、成形直後品および、成形後４０℃×５０ＲＨ％の雰囲気下で９０日間放置品について行った。
【００２９】
なお、成形直後の着色性は、成形直後の反射ｂ値が５．０以下、更には４．０以下であれば好適であるとみなせる。更に、経時的な色調変化は、その指標である色調の変化率（放置後の反射ｂ値／成形直後の反射ｂ値）が１．２以下、更には１．１以下であれば、好適であるとみなせる。
（２）酸素ガス透過度
ＡＳＴＭ−Ｄ−３９８５に記載の方法に準拠してＭＯＣＯＮＯＸＴＲＡＮ−１００（ＭＯＣＯＮ社製型式ＯＸ−ＴＲＡＮ２００Ｈ）を測定装置として使用する。測定温度は２３℃で測定サンプルとしては、薄膜を１２０ｍｍ×１２０ｍｍの大きさに切り出したものを用いる。酸素ガス透過度は測定後に厚みで１１μｍあたりの値になるように換算した数値を用いる。
【００３０】
（３）引張弾性率
ＡＳＴＭ−Ｄ−８８２に記載の方法に準拠して、テンシロンＵＴＭＩＩＩ−１００を測定装置として使用する。測定は２８℃で１ヶ月間エージング処理した薄膜を、幅１０ｍｍに切り出した測定サンプルを用いて、２３℃の恒温室内で、５ｍｍ／ｍｉｎの引張速度、チャック間距離１００ｍｍの条件で２％伸長時の荷重から測定値を計算する。数値としては薄膜の押出方向及びそれと直角方向についてそれぞれ測定し、両方向の平均値を採用する。
（４）押出生産性
インフレーションバブル法により薄膜を成形する時の押出生産性について、比較例１を△とし、これと比較して生産性の高いものから◎、○、△、×とした。
なお、実施例および比較例の各結果を表１にまとめ、ＵＶ値とＮＭＲ値との関係を示す図１中に、実施例を●、比較例を×で記入した。
【００３１】
（５）厚み斑
インフレーションバブル法により得られた薄膜をサンプルとして、周方向（押出方向に直角な方向）に均等分割するように３０点の位置を選ぶ。各位置での厚みをダイアルゲージ（ＵＰＲＩＧＴＳＴＡＮＤＭＯＤＥＬＵＳ−２６：ＴＥＣＬＯＣＫ製）にて測定し、その平均値を求め、これを薄膜成形物の厚みとする。更に、３０点の測定値から、厚みの最大値と最小値を選び、それらの値から平均値を差し引いた値を平均値で割り、±％表示した値を厚み斑として採用する。
【００３２】
【実施例１】
塩化ビニリデン単位８９重量％、塩化ビニル１１重量％の組成であり、重量平均分子量９８，０００（数平均分子量３９，０００）の共重合体の粉体４ｋｇに対して、アセチルクエン酸トリブチル２００ｇ、エポキシ化アマニ油４０ｇ、これに脱イオン水１０ｋｇを加えてスラリー状態で、常温にて６０分間攪拌した。これを遠心式の脱水機で脱水し、熱風乾燥機を用いて５０℃で２０分間乾燥した。
【００３３】
こうして得られた塩化ビニリデン系共重合体粉末を３７ｍｍ口径の完全噛合型同方向回転二軸押出機にて、スクリュー回転数１００回転、スクリュー先端の樹脂温度が１７７±１℃の条件で溶融し、直接サーキュラーダイを通じて、約４００μｍの厚みの筒状薄膜成形物を押出し、さらにインフレーションバブル法により成形し、薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
【００３４】
この薄膜のＵＶ値は、０．６１、ＮＭＲ値は、１．４×１０^-4、成形後の反射ｂ値は２．６、放置後の反射ｂ値は２．９、その変化率は１．１２、引張弾性率は４８００ｋｇ／ｃｍ²、酸素ガス透過度は４５ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は◎、厚みは１１±０．４μｍ、厚み斑は±３．６％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００３５】
【実施例２】
実施例１と同じ塩化ビニリデン系共重合体粉末を用いて、スクリュー回転数を８０回転、スクリュー先端の樹脂温度を１７５±１℃の条件とする他は実施例１と同様な方法で薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．５１、ＮＭＲ値は０．４×１０^-4、成形後の反射ｂ値は１．８、放置後の反射ｂ値は２．０、その変化率は１．１１、引張弾性率は４７００ｋｇ／ｃｍ²、酸素ガス透過度は４４ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は◎、厚みは１０．６±０．３μｍ、厚み斑は±２．８％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００３６】
【実施例３】
実施例１と同じ塩化ビニリデン系共重合体粉末を用いて、スクリュー回転数を１２０回転、スクリュー先端の樹脂温度を１７９±１℃の条件とする他は実施例１と同様な方法で薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．６８、ＮＭＲ値は１．８×１０^-4、成形後の反射ｂ値は３．１、放置後の反射ｂ値は３．３、その変化率は１．０６、引張弾性率は４６００ｋｇ／ｃｍ²、酸素ガス透過度は５０ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は◎、厚みは１１．１±０．４μｍ、厚み斑は±３．６％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００３７】
【実施例４】
アセチルクエン酸トリブチルを２８０ｇとする他は実施例１と同じ塩化ビニリデン系共重合体粉末を用いて、スクリュー回転数を１１０回転、スクリュー先端の樹脂温度を１７６±１℃の条件とする他は実施例１と同様な方法で薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．５８、ＮＭＲ値は０．９×１０^-4、成形後の反射ｂ値は２．５、放置後の反射ｂ値は２．８、その変化率は１．１２、引張弾性率は３７００ｋｇ／ｃｍ²、酸素ガス透過度は７０ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は○、厚みは１１．２±０．５μｍ、厚み斑は±４．５％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００３８】
【実施例５】
実施例１と同じ塩化ビニリデン系共重合体粉末を用いて、スクリュー回転数を１５０回転、スクリュー先端の樹脂温度を１８１±２℃の条件とする他は実施例１と同様な方法で薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．７４、ＮＭＲ値は２．９×１０^-4、成形後の反射ｂ値は３．７、放置後の反射ｂ値は４．１、その変化率は１．１１、引張弾性率は４２００ｋｇ／ｃｍ²、酸素ガス透過度は５０ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は○、厚みは１２．０±０．４μｍ、厚み斑は±３．３％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００３９】
【実施例６】
実施例１と同じ塩化ビニリデン系共重合体粉末を用いて、スクリュー回転数を１６０回転、スクリュー先端の樹脂温度を１８３±２℃の条件とする他は実施例１と同様な方法で薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．８９、ＮＭＲ値は３．４×１０^-4、成形後の反射ｂ値は４．６、放置後の反射ｂ値は４．９、その変化率は１．０７、引張弾性率は４２００ｋｇ／ｃｍ²、酸素ガス透過度は５２ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は○、厚みは１１．８±０．５μｍ、厚み斑は±４．２％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００４０】
【参考例１】
実施例１と同じ塩化ビニリデン系共重合体粉末を用いて、スクリュー回転数を１８０回転、スクリュー先端の樹脂温度を１８５±２℃の条件とする他は実施例１と同様な方法で薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．９２、ＮＭＲ値は５．１×１０^-4、成形後の反射ｂ値は５．２、放置後の反射ｂ値は６．１、その変化率は１．１８、引張弾性率は４８００ｋｇ／ｃｍ²、酸素ガス透過度は５５ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は○、厚みは１２．２±０．５μｍ、厚み斑は±４．１％であった。表１に示す通り、比較例に比べて着色の少ない薄膜が得られた。
【００４１】
【比較例１】
実施例１と同様の組成の塩化ビニリデン系共重合体粉体に同一条件にて添加剤ブレンド、乾燥を行う。この塩化ビニリデン共重合体粉末を単軸押出機にてスクリュー先端部の樹脂温度が１７６±２℃の範囲にて溶融し、直接サーキュラーダイを通じて、約４００μｍの厚みの筒状薄膜成形物を押出し、さらにインフレーションバブル法により成形し、薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
この薄膜のＵＶ値は０．６６、ＮＭＲ値は０．５×１０^-4、成形後の反射ｂ値は３．０、放置後の反射ｂ値は３．７、その変化率は１．２３、引張弾性率は４６００ｋｇ／ｃｍ²、酸素ガス透過度は５２ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は△、厚みは１１．５±０．７μｍ、厚み斑は±６．１％であった。表１に示す通り、成形直後の着色性は良好であるものの、経時的な色調変化が大きかった。
【００４２】
【比較例２】
比較例１と同じ原料を用いて、スクリュー先端の樹脂温度を１８５±２℃とする他は比較例１と同様な方法にて薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
得られた薄膜のＵＶ値は０．８４、ＮＭＲ値は１．２×１０^-4、成形後の反射ｂ値は４．３、放置後の反射ｂ値は５．０、その変化率は１．２３、引張弾性率は４３００ｋｇ／ｃｍ²、酸素ガス透過度は５８ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は△、厚みは１１．８±０．６μｍ、厚み斑は±５．１％であった。表１に示す通り、実施例に比べて薄膜の着色度合いが大きかった。
【００４３】
【比較例３】
比較例１と同じ原料を用いて、スクリュー先端の樹脂温度を１８２±２℃とする他は比較例１と同様な方法にて薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
得られた薄膜のＵＶ値は０．８８、ＮＭＲ値は２．４×１０^-4、成形後の反射ｂ値は５．０、放置後の反射ｂ値は６．１、その変化率は１．２２、引張弾性率は４４００ｋｇ／ｃｍ²、酸素ガス透過度は６０ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は△、厚みは１２．５±０．７μｍ、厚み斑は±５．６％であった。表１に示す通り、実施例に比べて薄膜の着色度合いが大きかった。
【００４４】
【比較例４】
比較例１と同じ原料を用いて、スクリュー先端の樹脂温度を１９０±２℃とする他は比較例１と同様な方法にて薄膜（塩化ビニリデン系樹脂の樹脂組成比：塩化ビニリデン部分８９重量％、塩化ビニル部分１１重量％）を得た。
得られた薄膜のＵＶ値は１．２、ＮＭＲ値は３．５×１０^-4、成形後の反射ｂ値は６．０、放置後の反射ｂ値は７．２、その変化率は１．２０、引張弾性率は４２００ｋｇ／ｃｍ²、酸素ガス透過度は６４ｃｃ／（ｍ²・２４ｈ・ａｔｍ）、押出生産性は×、厚みは１１．２±０．８μｍ、厚み斑は±７．１％であった。表１に結果を示す通り、実施例に比べて薄膜の着色度合いが大きかった。
【００４５】
【表１】

【００４６】
【発明の効果】
本発明によれば、塩化ビニリデンと塩化ビニルからなる共重合体において溶融加工時の脱塩酸によって生成する二重結合の共役性を制御し、ＵＶ値とＮＭＲ値とを特定の範囲とすることで、着色性が著しく改善された成形物を得ることができる。
【図面の簡単な説明】
【図１】薄膜成形体のＮＭＲ値とＵＶ値の関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film molded article used for a film, a sheet container or the like excellent in oxygen barrier properties, moisture resistance, etc. used for foods, pharmaceutical packaging materials and the like. More specifically, the present invention relates to a resin thin film molded article made of a copolymer of vinylidene chloride and vinyl chloride with improved color tone.
[0002]
[Prior art]
Vinylidene chloride resins are widely used for packaging materials because of their excellent oxygen barrier properties and moisture resistance. In addition, for direct extrusion molding of vinylidene chloride resin thin film moldings, Japanese Patent Publication No. Hei 4-501580 discloses, “For the extrusion processing of vinylidene chloride copolymer (copolymer), a single-screw or multi-screw extruder is used. In particular, single screw extruders are often used for heat-sensitive copolymers such as vinylidene chloride copolymers, "and so on. ing. In Japanese Patent Publication No. Hei 3-504023, as a device for melt-processing a thermosensitive polymer comprising a polymer composition containing a polyvinylidene chloride copolymer, a heated two-roll blender, a Brabender mixer, a Banbury mixer, a single unit It is described that a screw extruder, a twin screw extruder, or the like is used, and in the examples, a powder mixture is used as a Leistritz Model No. Extrusion is described in a 34 mm twin screw compounding extruder LSM-30.40. This extruder is a small-sized experimental multi-extruder whose two screw rotation directions can be rearranged in different directions or in the same direction, but the details are described in the publication. In general, it is classified as a different direction rotation type. In addition, this different-direction rotating twin-screw extruder is a commonly used type of polyvinyl chloride resin, but in this publication, it is used for pelletizing, and a thin film molded product is directly molded from the extruder. Not what you want. In fact, in the examples of the above publication, it is described that a single screw extruder having a screw diameter of 2.5 inches is used for forming a tape-like extrudate after pelletization.
[0003]
However, vinylidene chloride resins have a drawback that they are more susceptible to thermal deterioration during melt processing than thermoplastic resins such as general polyethylene. Due to these disadvantages, color change during molding processing (of molded products) Coloring) and the allowable range of molding conditions are narrow, and in particular, coloring of molded products has been a serious problem in applications requiring transparency. Furthermore, in the molding of vinylidene chloride resin thin film moldings, powdery raw materials are extruded, so when a single screw extruder is used, conveyance spots in the solid conveyance section are likely to occur, and the thin film moldings. Wrinkles were generated when the film was wound, and there were problems such as inferior handleability due to an elastic difference in the obtained thin film molded product.
[0004]
In order to improve the thermal stability during molding of such vinylidene chloride resins, various additives have been studied as described in Japanese Patent Publication No. 62-57663, etc. The additive which suppresses a change and the effect expresses by addition of a very small amount has not yet been found, and has responded by increasing the amount of various additives. However, increasing the amount of the additive reduces the oxygen barrier property, which is the original characteristic of vinylidene chloride resin, and in the case of a thin film shaped product, it is added to the surface of the thin film by adding a large amount. The agent bleeds out and causes problems such as stickiness and dusting on the surface of the thin film. Therefore, there is a limit to the improvement of heat deterioration by the additive.
[0005]
Japanese Patent Application Laid-Open No. 9-77827 discloses an investigation of the resin structure of a vinylidene chloride-based resin molded product. In this publication, in order to obtain a molded product having a high degree of crystallinity, the formula — (CH₂-CCl₂-CH = Cl-CH₂-CCl₂It is described that a resin containing 0.001 to 0.02% by weight of a unit represented by (-)-is used. However, the invention described in this publication pays attention to the crystallinity of the molded product, and is not intended to improve the thermal deterioration during the melt processing. Further, it was molded using a single screw extruder as in the conventional method, and the degree of coloring of the molded product was not sufficient.
[0006]
[Problems to be solved by the invention]
The first object of the present invention is to overcome the disadvantages of the prior art and provide a vinylidene chloride-based resin thin film molded product with less coloration. More specifically, the oxygen barrier property, which is the original characteristic of vinylidene chloride resin, An object of the present invention is to provide a vinylidene chloride-based resin thin film molded product with less coloring without deteriorating physical properties such as tensile elastic modulus.
The second object of the present invention is to provide a production method capable of stably supplying a vinylidene chloride-based resin thin film molded product with little coloring.
[0007]
[Means for Solving the Problems]
In order to overcome the drawbacks of the prior art and provide a thin colored molded product, the present inventors have investigated the behavior of dehydrochlorination, which is a major factor of color change due to thermal deterioration of vinylidene chloride resin. went. At that time, the present inventors not only improve the colorability immediately after molding, but also improve the coloration immediately after molding in order to provide a thin film molded product with little coloration at the time when it is finally available to consumers. We focused on the importance of improving the color change. And, by controlling the degree of conjugation of the double bonds generated in the resin by dehydrochlorination during melt processing, the thin film after processing is made to have a UV value and NMR value within a specific range. The present inventors have found that the color tone change of a molded product can be suppressed, and have reached the present invention.
[0008]
  That is, the present invention provides the following:(1) and (2)It is.
(1) From a copolymer comprising 70 to 95% by weight of vinylidene chloride and 5 to 30% by weight of vinyl chlorideManufactured by a manufacturing method including a step of extrusion molding using a fully meshing type co-rotating twin screw extruderWith vinylidene chloride resin thin film moldingsThere, UV value is0.4-0.9, NMR value is0.1 × 10 ^-Four ~ 3.5 × 10 ^-FourAnd the relationship between UV value and NMR value is UV value ≦ 1.65 × 10^ThreeX NMR value + 0.45 in the range, vinylidene chloride resin thin film molded product characterized by the above-mentioned.
(2)The copolymer comprising 70 to 95% by weight of vinylidene chloride and 5 to 30% by weight of vinyl chloride is melt-processed using a fully meshed co-rotating twin screw extruder. A method for producing a vinylidene chloride-based resin thin film molding.
[0009]
Hereinafter, the present invention will be described in detail.
The thin film molded product as used in the present invention is one having a thickness in the range of 5 μm to 2 mm, and is usually applied to all of films and sheets. Among these, it is suitably applied to a film having a thickness of 5 μm to 30 μm.
The vinylidene chloride resin constituting the molded product of the present invention is a copolymer resin of vinylidene chloride monomer and vinyl chloride monomer, and the composition ratio of the resin portion is 70 to 95% by weight of vinylidene chloride portion, The vinyl portion is 5 to 30% by weight. If the content of the vinylidene chloride moiety is less than 70% by weight, the characteristic properties of the molded product mainly composed of vinylidene chloride such as oxygen-blocking property and moisture-proof property are remarkably impaired. Since the decomposition point of the coalescence and the molding temperature are close to each other and the melt moldability is remarkably lowered, its use is limited. In view of its performance and moldability, the vinylidene chloride portion is preferably in the range of 80 to 95% by weight. In this copolymer, vinylidene chloride moieties are present in blocks in the resin, and the average number of blocks of vinylidene chloride moieties is 2 or more.
[0010]
Moreover, it is preferable that the weight average molecular weights of this resin are 5,000-500,000, More preferably, it is the range of 50,000-100,000. When the weight average molecular weight is less than 5,000, the mechanical strength of the molded product is lowered. When the weight average molecular weight is more than 500,000, the melt processability is lowered, so that its use is limited. Moreover, it is preferable that ratio of a weight average molecular weight and a number average molecular weight exists in the range of 1.1-5. This weight average molecular weight and number average molecular weight are gel permeation chromatography using tetrahydrofuran (hereinafter abbreviated as THF) as a solvent, dissolving the resin at a concentration of 0.05% by weight, and using monodisperse polystyrene having a known molecular weight as a standard substance. A value measured by a graph method (using GPC8000 series manufactured by Tosoh Corporation) is adopted.
[0011]
The vinylidene chloride resin of the present invention can employ a known polymerization method, and is preferably polymerized by a so-called suspension polymerization method.
Further, various additives such as a heat stabilizer and a plasticizer can be appropriately selected from known ones as long as the desired properties are not changed and within the scope of the present invention. Examples of such additives include acetyl tributyl citrate, dibutyl sebacate, polyethylene glycol fatty acid esters, acetylated monoglycerides, epoxidized linseed oil, epoxidized soybean oil and the like. The addition amount of the additive is preferably 1 to 12% by weight, more preferably 1 to 10% by weight, and further 2 to 8% by weight with respect to the resin from the viewpoints of oxygen barrier properties, moisture resistance, tensile elastic modulus and the like. %.
[0012]
  The molded product of the present invention has a UV value of0.4-0.9, NMR value is0.1 × 10 ^-Four ~ 3.5 × 10 ^-FourAnd the relationship between UV value and NMR value is UV value ≦ 1.65 × 10^ThreeIt is essential to be in the range of × NMR value + 0.45.
  As the UV value in the present invention, a value obtained by the following method is adopted. First, 1.00 g of a resin molded product is collected, mixed with 100 cc of tetrahydrofuran (THF) for spectroscopic analysis, which is a measurement solvent, in a sealed container, kept at 50 ° C., and uniformed with a shaker for 1 hour. Dissolve. Next, the solution is put into a standard quartz cell for ultraviolet absorption spectroscopy (optical path length: 10 mm, transmission plane: 2 surfaces), and a THF solution alone is used as a measurement blank cell, and a measurement device for ultraviolet absorption spectroscopy (“UV2100” light source manufactured by Shimadzu Corporation) is used. Measure the absorbance in the range from 500 nm to 190 nm with a deuterium lamp, the scanning speed is medium, the slit width is 2.00 nm, and the measuring device atmosphere temperature is 23 ° C. Of this absorbance, the absorbance value at 240 nm is defined as the UV value.
[0013]
The NMR value in the present invention is-(CH when the weight of the vinylidene chloride resin constituting the molded product of the present invention is 100.₂-CCl₂)-(CH = CCl)-(CH₂-CCl₂)-Defined as the proportion of protons of-(CH = CCl)-in the chain, and the value determined by the following method is adopted. First, 50 mg of a resin molded product is collected, put into a sample tube, and 1 g of deuterated THF as a measurement solvent is added and dissolved uniformly. Measurement is performed with a high-resolution proton nuclear magnetic resonance apparatus (“α-400” manufactured by JEOL Ltd.). The conditions are a measurement time of 2 seconds, an interval time of 5 seconds, and an integration count of 1000, and a spectrum with the horizontal axis representing the chemical shift with reference to tetramethylsilane is obtained. Of these, -CH₂Paying attention to a signal of 2.0 to 4.2 ppm which is a signal region of proton of −, a signal of 2.4 to 2.6 ppm is converted to —CH₂-CCl₂-CH₂-CCl₂-Proton of -3.0 to 3.4 ppm of signal -CH₂-CCl₂-CH₂A signal of 3.7 to 4.2 ppm is sent to the proton of -CHCl-₂-CHCl-CH₂First, the resin composition ratio (ratio of vinylidene chloride portion to vinyl chloride portion) of the thin film molding is determined from the spectral area values of these signals (the area of peaks in the NMR spectrum) assigned to the protons of —CHCl—.
[0014]
Next, the spectral area value of the signal of 4.4 to 5.2 ppm derived from the proton of -CHCl- of the vinyl chloride moiety, and-(CH₂-CCl₂)-(CH = CCl)-(CH₂-CCl₂The weight ratio of both protons is determined from the spectral area value of the 7.01 ppm singlet peak derived from the — (CH═CCl) — proton in the chain. From this weight ratio and the above resin composition ratio (ratio of vinyl chloride part and vinylidene chloride part),-(CH₂-CCl₂)-(CH = CCl)-(CH₂-CCl₂)-Determine the weight percentage of protons of-(CH = CCl)-in the chain.
[0015]
In general, it is said that the cause of coloration of vinyl chloride-based resins, vinylidene chloride resins and thin film moldings thereof is mainly that double bonds after dehydrochlorination contained in the resin form a conjugated system. Therefore, in order to essentially prevent the resin from being colored, it is very important not to grow this conjugated system of double bonds.
As described above, the UV value in the present invention adopts the absorbance value at 240 nm, corresponds to the amount of double bonds conjugated to about 3 to 4, and is a value strongly correlated with the coloring of the molded product. is there. The NMR value corresponds to the amount of double bonds dehydrochlorinated from the central vinylidene chloride part of the three-chain block of vinylidene chloride in the molecular chain, that is, the amount of isolated double bonds. It is an index that does not affect the coloring.
[0016]
The UV value of the molded product of the present invention is 0.2 to 1.5, and is preferably 0.4 to 0.9, more preferably 0.45 to 0.85 from the viewpoint of suppressing coloring of the molded product. More preferably, it is 0.5 to 0.8. A UV value of less than 0.2 does not substantially occur in a resin composition containing an additive suitable for melt processing within the scope of the present invention, and a value exceeding 1.5 has a large degree of coloring of a thin film molded product. Limited to be.
[0017]
The NMR value of the molded product of the present invention is 0.1 × 10.^-Four~ 6.4 × 10^-FourAnd preferably 0.1 × 10^-Four~ 3.5 × 10^-FourAnd more preferably 0.2 × 10^-Four~ 3x10^-Four, More preferably 0.3 × 10^-Four~ 2x10^-FourIt is. 0.1 × 10 of the lower limit of the NMR value^-FourIs a value necessary for ensuring uniformity of the structure of the microscopic molecular chain. The upper limit of 3.5 × 10^-FourIf it exceeds 1, it tends to shift to the formation of a conjugated double bond, and as a result, the degree of coloring increases, so that it is limited.
[0018]
Furthermore, the molded product of the present invention has a relationship between the UV value and the NMR value,
UV value ≦ 1.65 × 10^Three× NMR value + 0.45
It is essential. From the viewpoint of the color change of the molded product over time, preferably the UV value ≦ 1.65 × 10.^Three× NMR value + 0.425, more preferably UV value ≦ 1.65 × 10^ThreeX NMR value + 0.4. UV and NMR values are even between 0.2 and 1.5 and 0.1 × 10 respectively^-Four~ 6.4 × 10^-FourIf the above relational expression is not satisfied even in this range, a sufficient molded product cannot be obtained in the color tone after molding or the color tone change over time.
[0019]
In the conventional molded product, when an isolated double bond is generated, a conjugated double bond is correspondingly increased, and a UV value and an NMR value are UV values> 1.65 × 10.^ThreeX NMR value +0.45 and the color tone changes significantly. On the other hand, the molded product of the present invention satisfying the above relational expression is thermally deteriorated by melt processing, and the generated double bond is likely to be a relatively isolated double bond and does not easily proceed to a conjugated double bond. I think that. That is, when the molded product of the present invention satisfies the above relational expression, it is considered that the ratio of the double bonds conjugated by dehydrochlorination generated by dehydrochlorination becomes relatively low during melt processing, and the degree of coloring is remarkably improved. It is done. Furthermore, in the molded product of the present invention, the color tone immediately after molding is good, and the color tone change with time due to aging of the molded product is small. This is because the molded product immediately after molding has relatively many isolated double bonds, so even if dehydrochlorination is performed over time due to aging or the like, it is difficult to grow a long-chain double bond conjugated system that leads to coloring. It is thought that.
[0020]
The said range in this invention is shown in FIG. In FIG. 1, the vertical axis represents the UV value of the thin film molded body, and the horizontal axis represents the NMR value. The hatched portion in FIG. 1 indicates the scope of the present invention.
Those within the scope of the present invention are good in terms of color tone as described above compared with those outside the range, and change in color tone such as discoloration after molding, and change in color tone over time are small. Further, in terms of film physical properties such as oxygen gas permeability and tensile elastic modulus, a good thin film is obtained, and productivity at the time of extrusion is also good. This is because, for example, the extrusion productivity such as mixing of heat-degraded products that impair the puncture frequency of the inflation bubble and the product quality when the thin film is obtained by the inflation bubble method which is a generally known vinylidene chloride resin thin film molding method is It is higher than the one out of range. Although there is no clear reason for this, from the microscopic point of view, the present invention has a high molecular chain uniformity, which is why the additive distribution is made uniform and local thermal degradation occurs. This is considered to have an effect of suppressing bubble puncture, and this is considered to have an effect on bubble puncture suppression.
[0021]
The molded product of the present invention is improved in color tone change and the like while maintaining the original properties of vinylidene chloride resin such as oxygen barrier properties. The molded product of the present invention has an oxygen gas permeability of 100 cc / (m measured by the method described later.²It is preferably 24 hrs · atm) or less.
As a production method for obtaining a thin film molded product within the above-mentioned range of the present invention, a copolymer having a resin composition ratio of 70 to 95% by weight of vinylidene chloride portion and 5 to 30% by weight of vinyl chloride portion is obtained by biaxial This can be achieved by melt processing using an extruder. Here, the twin screw extruder is a known extruder having two extrusion screws.
[0022]
As described above, a single-screw extruder has been conventionally used in direct extrusion molding of a vinylidene chloride-based resin thin film molding. On the other hand, in the present invention, a new thin film molded article having the above characteristics was successfully supplied by using a twin screw extruder, and further a specific twin screw extruder under specific conditions. Is. This is also clear from FIG. 1, which is a graph of Examples and Comparative Examples described later. That is, as shown in FIG. 1, the thin film moldings produced using a conventional single screw extruder are both out of the range of the UV value and the NMR value of the present invention, and therefore inferior in color tone change. Moreover, the extrusion productivity is inferior as shown in a comparative example described later.
[0023]
In order to perform the melt extrusion process in the present invention, it is possible to keep the extrusion temperature low by selecting a kneading disk and optimizing the screw rotation speed using a generally described twin-screw extruder. In particular, it is possible to obtain a molded product with less discoloration, which is the object of the present invention, by melting using a fully meshed co-rotating twin-screw extruder. Preferably, among the fully meshed co-rotating twin screw extruders, an extruder having a ratio L / D of the total screw length L to the screw diameter D in the range of 15 to 30 is used. Then, by adjusting the screw rotation speed and the barrel temperature, the melting is performed within the range of the resin temperature of 170 to 190 ° C, preferably 175 to 180 ° C of the extruder screw tip.
[0024]
By using a twin-screw extruder, it has a so-called “self-cleaning” property that scrapes out the trough of the screw flight at the crest of the screw flight, and prevents long-term deposits adhering to the wall surface of the screw flight. Can be considered. Further, when the raw material is melted, the screw configuration can be arbitrarily set in the twin-screw extruder, so that the melting at the kneading disk portion can be controlled to the optimum condition.
[0025]
In the production method of the present invention, the copolymer composition and average molecular weight of the vinylidene chloride resin to be used can be changed within the scope of the present invention, and the extrusion resin temperature can be kept lower. More specifically, this is achieved by blending a vinylidene chloride resin having a low average molecular weight to reduce the melt viscosity during processing and lowering the temperature of the extruded resin.
[0026]
Further, the present invention, as another invention, is a vinylidene chloride-based resin thin film molded product made of a copolymer comprising 70 to 95% by weight of vinylidene chloride portion and 5 to 30% by weight of vinyl chloride portion, and thickness variation is ± 5%. Less than, preferably less than ± 4.5%, more preferably ± 4. Also included is a vinylidene chloride-based resin thin film molded product having a thickness of 5 to 30 μm which is less than%. In this case, when the thickness unevenness is in the above range, a uniform roll without wrinkles or the like is obtained when the thin film molded product is wound, and an elastic difference occurs in a packaging film such as food. Because it is difficult, it produces effects such as excellent handleability. Such a thin film molded article can be provided for the first time by adopting the above method using a twin screw extruder.
[0027]
That is, in the twin-screw extruder, since the raw material powder is uniformly transported in the solid conveyance part, it is considered that the thickness unevenness can be achieved. The preferred UV value and NMR value range of the vinylidene chloride resin thin film molded product with the thickness unevenness of less than ± 5% are 0.2 to 1.5 (more than the reason for the same reason as in the first invention). Preferably 0.4 to 0.9, more preferably 0.45 to 0.85, most preferably 0.5 to 0.8), 0.1 × 10^-Four~ 6.4 × 10^-Four(More preferably 0.1 × 10^-Four~ 3.5 × 10^-FourAnd more preferably 0.2 × 10^-Four~ 3x10^-Four, Most preferably 0.3 × 10^-Four~ 2x10^-FourAnd the relationship between the UV value and the NMR value is UV value ≦ 1.65 × 10.^ThreeX NMR value + 0.45 is most preferable. The preferred additive and the amount added are the same as in the first invention.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described more specifically based on examples and comparative examples.
The molded product was evaluated by the following method.
(1) Coloring of molded products
The color of the copolymer molded product of the present invention is measured according to “Testing method for optical properties of plastic” (JISK7105). Measurement methods in Examples and Comparative Examples are shown below. Nippon Denshoku Industries Co., Ltd. Z-II type is used as a measuring device. The cylindrical part of the extruded cylindrical molded product is crushed into a flat sheet, and a measurement sample is collected. The color difference b value of the reflected light from the standard white surface is measured. The measurement was performed on the product immediately after molding and on the product left for 90 days in an atmosphere of 40 ° C. × 50 RH% after molding.
[0029]
In addition, it can be considered that the colorability immediately after molding is suitable if the reflection b value immediately after molding is 5.0 or less, and further 4.0 or less. Furthermore, the color tone change over time is suitable if the color tone change rate (reflected b value after standing / reflected b value immediately after molding) as an index is 1.2 or less, further 1.1 or less. It can be considered that there is.
(2) Oxygen gas permeability
In accordance with the method described in ASTM-D-3985, MOCON OXTRAN-100 (model OX-TRAN 200H manufactured by MOCON) is used as a measuring device. A measurement temperature is 23 ° C., and a measurement sample obtained by cutting a thin film into a size of 120 mm × 120 mm is used. For the oxygen gas permeability, a numerical value converted so as to be a value per 11 μm in thickness after measurement is used.
[0030]
(3) Tensile modulus
In accordance with the method described in ASTM-D-882, Tensilon UTIIIIII-100 is used as a measuring device. Measurement was performed at 2% elongation under conditions of a tensile rate of 5 mm / min and a distance between chucks of 100 mm in a constant temperature room at 23 ° C. using a measurement sample cut out to a width of 10 mm from a thin film aged at 28 ° C. for 1 month. Calculate the measured value from the load. As numerical values, measurements are made in the extrusion direction of the thin film and in the direction perpendicular thereto, and the average value in both directions is adopted.
(4) Extrusion productivity
Regarding the extrusion productivity when forming a thin film by the inflation bubble method, Comparative Example 1 was evaluated as Δ, and from the highest productivity compared to this, ◎, ○, Δ, ×.
The results of the examples and comparative examples are summarized in Table 1, and in FIG. 1 showing the relationship between the UV values and the NMR values, the examples are indicated by ● and the comparative examples are indicated by x.
[0031]
(5) Thick spots
Using the thin film obtained by the inflation bubble method as a sample, the positions of 30 points are selected so as to be equally divided in the circumferential direction (direction perpendicular to the extrusion direction). The thickness at each position is measured with a dial gauge (UPRIGT STAND MODEL US-26: manufactured by TECLOCK), the average value is obtained, and this is taken as the thickness of the thin film molded product. Furthermore, the maximum value and the minimum value of the thickness are selected from the measured values at 30 points, the value obtained by subtracting the average value from these values is divided by the average value, and the value displayed ±% is adopted as the thickness unevenness.
[0032]
[Example 1]
It is composed of 89% by weight of vinylidene chloride unit and 11% by weight of vinyl chloride, and 4 kg of copolymer powder having a weight average molecular weight of 98,000 (number average molecular weight 39,000), 200 g of tributyl acetylcitrate, epoxy 40 g of linseed oil and 10 kg of deionized water were added thereto and stirred in a slurry state at room temperature for 60 minutes. This was dehydrated with a centrifugal dehydrator and dried at 50 ° C. for 20 minutes using a hot air drier.
[0033]
The vinylidene chloride copolymer powder thus obtained was melted in a 37 mm diameter fully meshed co-rotating twin screw extruder under the conditions that the screw rotation speed was 100 and the resin temperature at the screw tip was 177 ± 1 ° C. A cylindrical thin film molded product having a thickness of about 400 μm is extruded through a direct circular die, and further molded by an inflation bubble method to form a thin film (resin composition ratio of vinylidene chloride resin: 89% by weight of vinylidene chloride, 11% by weight of vinyl chloride) )
[0034]
The UV value of this thin film is 0.61, and the NMR value is 1.4 × 10.^-FourThe reflection b value after molding is 2.6, the reflection b value after standing is 2.9, the rate of change is 1.12, and the tensile modulus is 4800 kg / cm.²The oxygen gas permeability is 45 cc / (m²24 h · atm), extrusion productivity was ◎, thickness was 11 ± 0.4 μm, and thickness unevenness was ± 3.6%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0035]
[Example 2]
Using the same vinylidene chloride copolymer powder as in Example 1, using the same method as in Example 1 except that the screw rotation speed is 80 rotations and the resin temperature at the screw tip is 175 ± 1 ° C. Resin composition ratio of vinylidene resin: 89% by weight of vinylidene chloride portion and 11% by weight of vinyl chloride portion).
The UV value of this thin film is 0.51, and the NMR value is 0.4 × 10.^-FourThe reflection b value after molding is 1.8, the reflection b value after standing is 2.0, the rate of change is 1.11, and the tensile modulus is 4700 kg / cm.²The oxygen gas permeability is 44 cc / (m²24 h · atm), extrusion productivity was ◎, thickness was 10.6 ± 0.3 μm, and thickness unevenness was ± 2.8%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0036]
[Example 3]
Using the same vinylidene chloride copolymer powder as in Example 1, using the same method as in Example 1, except that the screw rotation speed was 120 rotations and the resin temperature at the screw tip was 179 ± 1 ° C. Resin composition ratio of vinylidene resin: 89% by weight of vinylidene chloride portion and 11% by weight of vinyl chloride portion).
The UV value of this thin film was 0.68, and the NMR value was 1.8 × 10.^-FourThe reflection b value after molding is 3.1, the reflection b value after standing is 3.3, the rate of change is 1.06, and the tensile modulus is 4600 kg / cm.²The oxygen gas permeability is 50 cc / (m²24 h · atm), extrusion productivity was ◎, thickness was 11.1 ± 0.4 μm, and thickness unevenness was ± 3.6%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0037]
[Example 4]
Other than using 280 g of tributyl acetylcitrate, the same vinylidene chloride copolymer powder as in Example 1 was used, except that the screw rotation speed was 110 rotations and the resin temperature at the screw tip was 176 ± 1 ° C. A thin film (resin composition ratio of vinylidene chloride resin: 89% by weight of vinylidene chloride and 11% by weight of vinyl chloride) was obtained in the same manner as in Example 1.
The UV value of this thin film is 0.58, and the NMR value is 0.9 × 10.^-FourThe reflection b value after molding is 2.5, the reflection b value after standing is 2.8, the rate of change is 1.12, and the tensile modulus is 3700 kg / cm.²The oxygen gas permeability is 70 cc / (m²24 h · atm), extrusion productivity was ○, thickness was 11.2 ± 0.5 μm, and thickness unevenness was ± 4.5%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0038]
[Example 5]
Using the same vinylidene chloride copolymer powder as in Example 1, using the same method as in Example 1 except that the screw rotation speed is 150 rotations and the resin temperature at the screw tip is 181 ± 2 ° C. Resin composition ratio of vinylidene resin: 89% by weight of vinylidene chloride portion and 11% by weight of vinyl chloride portion).
The thin film had a UV value of 0.74 and an NMR value of 2.9 × 10.^-FourThe reflection b value after molding is 3.7, the reflection b value after standing is 4.1, the rate of change is 1.11, and the tensile modulus is 4200 kg / cm.²The oxygen gas permeability is 50 cc / (m²24 h · atm), the extrusion productivity was ○, the thickness was 12.0 ± 0.4 μm, and the thickness unevenness was ± 3.3%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0039]
[Example 6]
Using the same vinylidene chloride copolymer powder as in Example 1, using the same method as in Example 1, except that the screw rotation speed was 160 rotations and the resin temperature at the screw tip was 183 ± 2 ° C. Resin composition ratio of vinylidene resin: 89% by weight of vinylidene chloride portion and 11% by weight of vinyl chloride portion).
The thin film had a UV value of 0.89 and an NMR value of 3.4 × 10.^-FourThe reflection b value after molding is 4.6, the reflection b value after standing is 4.9, the rate of change is 1.07, and the tensile modulus is 4200 kg / cm.²The oxygen gas permeability is 52 cc / (m²24 h · atm), the extrusion productivity was ○, the thickness was 11.8 ± 0.5 μm, and the thickness unevenness was ± 4.2%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0040]
[Reference example 1]
  Using the same vinylidene chloride copolymer powder as in Example 1, using the same method as in Example 1 except that the screw rotation speed is 180 rotations and the resin temperature at the screw tip is 185 ± 2 ° C. Resin composition ratio of vinylidene resin: 89% by weight of vinylidene chloride portion and 11% by weight of vinyl chloride portion).
  The thin film has a UV value of 0.92 and an NMR value of 5.1 × 10 5.^-FourThe reflection b value after molding is 5.2, the reflection b value after standing is 6.1, the rate of change is 1.18, and the tensile modulus is 4800 kg / cm.²The oxygen gas permeability is 55 cc / (m²24 h · atm), the extrusion productivity was ○, the thickness was 12.2 ± 0.5 μm, and the thickness unevenness was ± 4.1%. As shown in Table 1, a thin film with less coloring compared to the comparative example was obtained.
[0041]
[Comparative Example 1]
The vinylidene chloride copolymer powder having the same composition as in Example 1 is blended and dried under the same conditions. This vinylidene chloride copolymer powder was melted in a single screw extruder at a screw tip resin temperature in the range of 176 ± 2 ° C., and a cylindrical thin film molded product having a thickness of about 400 μm was extruded directly through a circular die, Furthermore, it shape | molded by the inflation bubble method, and obtained the thin film (Resin composition ratio of vinylidene chloride resin: 89 weight% of vinylidene chloride parts, 11 weight% of vinyl chloride parts).
The UV value of this thin film is 0.66, and the NMR value is 0.5 × 10.^-FourThe reflection b value after molding is 3.0, the reflection b value after standing is 3.7, the rate of change is 1.23, and the tensile modulus is 4600 kg / cm.²The oxygen gas permeability is 52 cc / (m²24 h · atm), the extrusion productivity was Δ, the thickness was 11.5 ± 0.7 μm, and the thickness unevenness was ± 6.1%. As shown in Table 1, although the colorability immediately after molding was good, the color tone change over time was large.
[0042]
[Comparative Example 2]
A thin film (resin composition ratio of the vinylidene chloride resin: 89% by weight of vinylidene chloride resin) was used in the same manner as in Comparative Example 1, except that the same raw material as in Comparative Example 1 was used and the resin temperature at the screw tip was 185 ± 2 ° C. , 11% by weight of vinyl chloride portion).
The obtained thin film had a UV value of 0.84 and an NMR value of 1.2 × 10.^-FourThe reflection b value after molding is 4.3, the reflection b value after standing is 5.0, the rate of change is 1.23, and the tensile modulus is 4300 kg / cm.²The oxygen gas permeability is 58 cc / (m²24 h · atm), the extrusion productivity was Δ, the thickness was 11.8 ± 0.6 μm, and the thickness unevenness was ± 5.1%. As shown in Table 1, the degree of coloring of the thin film was larger than that of the example.
[0043]
[Comparative Example 3]
A thin film (resin composition ratio of the vinylidene chloride resin: 89% by weight of vinylidene chloride resin) was used in the same manner as in Comparative Example 1 except that the same raw material as in Comparative Example 1 was used and the resin temperature at the screw tip was 182 ± 2 ° C. , 11% by weight of vinyl chloride portion).
The obtained thin film had a UV value of 0.88 and an NMR value of 2.4 × 10.^-FourThe reflection b value after molding is 5.0, the reflection b value after standing is 6.1, the rate of change is 1.22, and the tensile modulus is 4400 kg / cm.²The oxygen gas permeability is 60 cc / (m²24 h · atm), the extrusion productivity was Δ, the thickness was 12.5 ± 0.7 μm, and the thickness unevenness was ± 5.6%. As shown in Table 1, the degree of coloring of the thin film was larger than that of the example.
[0044]
[Comparative Example 4]
A thin film (resin composition ratio of vinylidene chloride resin: 89% by weight of vinylidene chloride resin) was used in the same manner as in Comparative Example 1, except that the same raw material as in Comparative Example 1 was used and the resin temperature at the screw tip was 190 ± 2 ° C. , 11% by weight of vinyl chloride portion).
The obtained thin film had a UV value of 1.2 and an NMR value of 3.5 × 10 6.^-FourThe reflection b value after molding is 6.0, the reflection b value after standing is 7.2, the rate of change is 1.20, and the tensile modulus is 4200 kg / cm.²The oxygen gas permeability is 64 cc / (m²24 h · atm), extrusion productivity was x, thickness was 11.2 ± 0.8 μm, and thickness unevenness was ± 7.1%. As shown in Table 1, the degree of coloring of the thin film was larger than that of the example.
[0045]
[Table 1]

[0046]
【The invention's effect】
According to the present invention, in the copolymer composed of vinylidene chloride and vinyl chloride, the conjugation property of the double bond generated by dehydrochlorination at the time of melt processing is controlled, and the UV value and the NMR value are set within a specific range. Thus, a molded product with significantly improved colorability can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the NMR value and UV value of a thin film molded article.

Claims

It is made of a copolymer comprising 70 to 95% by weight of vinylidene chloride and 5 to 30% by weight of vinyl chloride, and is produced by a production method including a step of extrusion using a fully meshed co- rotating twin screw extruder. a vinylidene chloride-based resin film molding, UV value 0.4 to 0.9, NMR value is in the range of ^{^{0.1 × 10 -4 ~3.5 × 10 -4}} , and UV value and NMR A vinylidene chloride resin thin film molded product characterized in that the relationship of values is in the range of UV value ≦ 1.65 × 10 ³ × NMR value + 0.45.

The copolymer comprising 70 to 95% by weight of vinylidene chloride and 5 to 30% by weight of vinyl chloride is melt-processed using a fully meshed co-rotating twin screw extruder. A method for producing a vinylidene chloride-based resin thin film molding.