JPS6344534B2 - - Google Patents
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- Publication number
- JPS6344534B2 JPS6344534B2 JP55028373A JP2837380A JPS6344534B2 JP S6344534 B2 JPS6344534 B2 JP S6344534B2 JP 55028373 A JP55028373 A JP 55028373A JP 2837380 A JP2837380 A JP 2837380A JP S6344534 B2 JPS6344534 B2 JP S6344534B2
- Authority
- JP
- Japan
- Prior art keywords
- tube
- film
- stretching
- temperature
- melt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001816 cooling Methods 0.000 claims description 37
- 239000004743 Polypropylene Substances 0.000 claims description 36
- -1 polypropylene Polymers 0.000 claims description 36
- 229920001155 polypropylene Polymers 0.000 claims description 36
- 238000004519 manufacturing process Methods 0.000 claims description 12
- 239000003507 refrigerant Substances 0.000 claims description 10
- 238000002425 crystallisation Methods 0.000 claims description 8
- 230000008025 crystallization Effects 0.000 claims description 8
- 239000002667 nucleating agent Substances 0.000 claims description 8
- 238000000034 method Methods 0.000 description 23
- 239000013078 crystal Substances 0.000 description 14
- 239000000110 cooling liquid Substances 0.000 description 9
- 230000003746 surface roughness Effects 0.000 description 8
- 239000003990 capacitor Substances 0.000 description 7
- 239000002826 coolant Substances 0.000 description 7
- 238000001125 extrusion Methods 0.000 description 7
- 238000009826 distribution Methods 0.000 description 6
- 239000000155 melt Substances 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 238000005470 impregnation Methods 0.000 description 5
- 239000002344 surface layer Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 239000011888 foil Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000012768 molten material Substances 0.000 description 3
- KSLLMGLKCVSKFF-UHFFFAOYSA-N 5,12-dihydroquinolino[2,3-b]acridine-6,7,13,14-tetrone Chemical compound N1C2=CC=CC=C2C(=O)C2=C1C(=O)C(C(=O)C1=CC=CC=C1N1)=C1C2=O KSLLMGLKCVSKFF-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052751 metal Chemical class 0.000 description 2
- 239000002184 metal Chemical class 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 102100027340 Slit homolog 2 protein Human genes 0.000 description 1
- 101710133576 Slit homolog 2 protein Proteins 0.000 description 1
- 229920006378 biaxially oriented polypropylene Polymers 0.000 description 1
- 239000011127 biaxially oriented polypropylene Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000013522 chelant Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000004049 embossing Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 229920001384 propylene homopolymer Polymers 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 210000003934 vacuole Anatomy 0.000 description 1
- 239000002759 woven fabric Substances 0.000 description 1
- 239000004711 α-olefin Substances 0.000 description 1
Landscapes
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
- Organic Insulating Materials (AREA)
Description
本発明は電気ケーブル、コンデンサ、トランス
などの油浸型電気用物品に用い得る優れた絶縁油
の含浸特性及び電気的特性を示す電気物品用ポリ
プロピレンフイルムの製造方法に関するものであ
る。
２軸延伸ポリプロピレンフイルムは従来用いら
れてきた絶縁紙に比べ極めて良好な絶縁耐力と誘
電特性を有しているため近年絶縁紙に代つて電気
ケーブル、コンデンサ、トランスなど小型軽量化
と長期耐久力を要求される各種電気物品に用いら
れるようになつた。特にコンデンサの場合電位傾
度、誘電率、絶縁耐圧などの観点から絶縁紙の使
用量を減少し、できるだけポリプロピレンフイル
ムの比率を高める傾向が強くなつている。ところ
でこのポリプロピレンフイルムの比率を高める場
合、特に絶縁紙を併用しない場合従来の２軸延伸
ポリプロピレンフイルムはその表面が平滑性に富
んでいるためフイルム面同志あるいは該フイルム
面とアルミニウム箔などの箔状電極面とが完全に
密着密閉されてしまうためコンデンサ素子内部に
取り込まれた空気あるいは水分を十分に除去し、
かつ絶縁油をフイルム表面と箔状電極層間に完全
に含浸させることが非常に困難であるため絶縁油
の未含浸部分によるコロナ発生電圧、コロナ消去
電圧、絶縁破壊電圧の低下を起しやすく、この結
果早期破壊を生じやすく十分な電気的特性を有す
る製品とすることができない欠点を有している。
かかる欠点を減少せしめる方法としては、例え
ばフイルムコンデンサ分野では従来のような絶縁
紙を併用する複合誘電体の他に、ポリプロピレン
フイルムにエンボス加工を施すことによりフイル
ム表面に凹凸を付与せしめ粗面化することにより
絶縁油の含浸性を向上せしめる方法が提案されて
いるが、かかる方法ではフイルム特性が低下しや
すく、また凹部への油の含浸性が逆に低下する欠
点を有している。またポリプロピレンに他のポリ
マーをブレンドしてフイルム化し延伸処理を施し
て粗面化する方法があるがブレンドするポリマー
の種類によつて電気的特性が著しく低下したり、
絶縁油の含浸性が十分満足するものが得られない
などの欠点を有している。さらに異種形態の結晶
を含有する未延伸フイルムを延伸することにより
フイルム表面に網目状構造を発現させる方法が提
案されているが、かかる方法によるフイルムは絶
縁油の含浸性は優れているが総合的な電気的特性
は未だ十分満足するものではない。即ち単なる網
目状構造のみによつてフイルム表面の含浸構造を
小さく、かつ深くし絶縁油の含浸量を確保するだ
けでは使用と共にこれらの構造がへたる為初期特
性が良くても経時的に性能が低下する所謂Ｖ―Ｔ
特性の点で必ずしも好ましい結果が得られない面
がある。
本発明者らはかかる現状に鑑み優れた誘電体特
性と絶縁油易含浸性を有する電気物品用ポリプロ
ピレンフイルムを得るべく鋭意検討した結果β型
結晶化核剤を添加しない結晶性ポリプロピレンを
特定温度範囲にて溶融押出成形して得られるチユ
ーブ状溶融体の内面を特定値以上の温度勾配因子
となるように冷却マンドレル上に接触摺動させる
と共に該溶融体の外面を特定温度の冷却媒体に晒
して得られるポリプロピレン未延伸成形物を特定
条件下で２軸延伸することにより主として繊維状
組織が重なり絡み合つて構成された周縁盛上り部
を有するクレーター状凹凸構造と襞状繊維状構造
とから構成される高密度に分布した粗面構造をフ
イルム表面に有し、且つ表面粗度５％以上なるフ
イルムが得られ、かかるフイルムが上記目的に適
うことを見出し本発明に到達した。
即ち本発明はβ型結晶化核剤を添加しない結晶
性ポリプロピレンを210〜250℃の温度範囲にてリ
ングダイより溶融押出してチユーブ状溶融体と
し、引続き該チユーブ状溶融体の内面を下記
（）式で定義される温度勾配因子（Ｙ）と得ら
れるチユーブ状未延伸成形物の厚み（Ｘ）との関
係が下記（）式を満足するように冷却マンドレ
ル上に接触摺動させると共に、該チユーブ状溶融
体の外面をT2℃以下の冷却媒体に晒し冷却し引
取ることにより得られるβ型結晶化核剤を含有し
ないポリプロピレン未延伸成形物を延伸開始点に
おける延伸温度が145〜176℃、一方向の延伸倍率
が８倍未満になる条件で２軸延伸することを特徴
とする電気物品用ポリプロピレンフイルムの製造
方法である。
Ｙ＝（T2−T1）×Ｒ／Ｌ ……（）
Ｙ＞4400／Ｘ ……（）
但し （）、（）式中
Ｙ：温度勾配因子（℃／秒）
T1：冷却マンドレル入口の冷媒温度（℃）
T2：冷却マンドレル出口の冷媒温度（℃）
Ｒ：チユーブの引取速度（cm／秒）
Ｌ：冷却マンドレルの実効長（cm）
Ｘ：未延伸成形物の厚さ（μ）
本発明を実施するに際して用いる結晶性ポリプ
ロピレンとしてはプロピレン単独重合体のみなら
ず少量の他のα―オレフインとの共重合体も含ま
れ、アイソタクテイシテイを表わすｎ―ヘプタン
沸点抽出８時間後の残渣が90％以上のアイソタク
テイツクポリプロピレンであり、その重合度とし
ては溶融成形が可能であればどの程度でもよいが
メルトインデツクスが0.5〜20のものが好ましい。
またキナクリドンキノン、置換キナクリドンキノ
ンあるいはこれらの金属キレート化合物等の特殊
なβ型結晶化核剤をポリプロピレンに添加したも
のを用いた場合得られるフイルム中に含まれる結
晶化核剤や結晶化核剤の影響によりフイルム内部
に生じた微細な空胞が本発明の電気物品用フイル
ムとしての特性を低下せしめるので本発明の実施
に際して使用する結晶性ポリプロピレン中には特
殊なβ型結晶化核剤が含まれていないものを用い
ることが必要である。
本発明のフイルムの製造方法の第１の特徴はポ
リプロピレン未延伸成形物を製造するに際してβ
型結晶化核剤を添加することなく結晶性ポリプロ
ピレンを特定温度範囲、即ち210〜250℃、好まし
くは210〜245℃の範囲で溶融押出成形してチユー
ブ状溶融体とすると共に、この溶融体を得ようと
する未延伸成形物の厚みに応じた特定の温度勾配
をかけてやるように冷却マンドレル上を接触摺動
させてやることによつて未延伸成形物外側表層部
にβ型結晶を発現させた点である。即ち冷却マン
ドレル使用による際のマンドレル冷却条件と未延
伸成形物の厚みとの関係及びβ型結晶の発現性と
の総合関係を究明したものである。また第２の特
徴はかかる表層部にβ型結晶を有する未延伸成形
物を特定の延伸条件下で２軸延伸することにより
フイルム表面上に上述した如き特異な粗面構造を
形成せしめた点である。
本発明を実施するに際しては結晶性ポリプロピ
レンを210〜250℃、好ましくは210〜245℃の温度
範囲にてリングダイより溶融押出してチユーブ状
溶融体とする。この溶融押出温度はβ型結晶核生
成と大きな関連があり、上記温度範囲にて溶融押
出されて初めてβ型結晶核が生成されるものと推
定され、上記温度範囲外にて溶融押出されたチユ
ーブ状溶融体は上記（）、（）式の条件を満足
するように成形しても好ましいものが得られな
い。
次に上記温度範囲にて溶融押出して得られたチ
ユーブ状溶融体の内面を冷却マンドレル上に接触
摺動させると共に、該チユーブ状溶融体の外面を
特定温度以下の冷却媒体に晒し引取つてチユーブ
状ポリプロピレン未延伸成形物とするわけである
が、これに際して冷却マンドレル入口、出口の各
冷媒温度、冷却マンドレルの実効長、チユーブ引
取速度によつて定まる上記（）式で示される温
度勾配因子（Ｙ）とチユーブ状未延伸成形物の厚
み（Ｘ）との関係が上記（）式を満足するよう
に冷却マンドレルの冷却条件、チユーブ引取速度
条件、未延伸成形物の厚み条件などの種々の条件
をコントロールしなければならない。ここで温度
勾配因子（Ｙ）はチユーブ状溶融体が引取方向に
毎秒何度の温度上昇を受けるかを示すものであり
チユーブ状未延伸成形物の外側の表層部に発現す
るβ型結晶量、サイズ及び分布とに密接な関係を
有するものである。また（）式で示される条件
は表面粗度が５％以上なるようなフイルムが得ら
れるのに十分なβ型結晶が発現する領域であり、
得ようとする未延伸成形物の厚み（Ｘ）によつて
必要とする温度勾配因子（Ｙ）を一義的に設定す
ることを容易ならしめたことはこれまでにない画
期的なことであり大きな特徴である。
本発明を実施するに際して用いる冷却マンドレ
ルは円筒状物でありその材質としては一般の金
属、セラミツク、ガラス、炭素又は高分子物質等
を用いることができ、該冷却マンドレル表面の形
状としては鏡面、梨地又は織物状とすることがで
きる。冷却マンドレル内部には上記温度勾配因子
を達成すべく冷媒の供給管、排出管を有してお
り、冷媒としては空気や水等の冷媒が好適に用い
られる。冷却マンドレルの実効長とはチユーブ状
溶融体の内面が接触摺動する際に実際に接触し始
める位置から引離れる位置迄の長さを示すもので
ある。
また本発明を実施するに際して上記チユーブ状
溶融体の外面を冷却マンドレル出口における冷媒
温度（T2）以下の冷却媒体に晒し冷却する方法
としては水冷法、空冷法その他の冷却方法を任意
に用いることができる。該溶融体の外面をT2を
超える温度の冷却媒体に晒し冷却した場合には有
効な温度勾配因子をもたらすことが困難となり最
終的には本発明の特異な粗面構造を有する電気物
品用フイルムとすることができなくなるので望ま
しくない。
本発明を実施するに際してのポリプロピレン未
延伸成形物を製造する実施態様の一例を図面に基
いて説明するが必ずしもこれに限定されるもので
はない。
まず結晶性ポリプロピレンを押出機に供給し
210〜250℃の温度範囲にて第１図のリングダイス
１の環状スリツト２より溶融押出してチユーブ状
溶融体３とする。次いで圧搾空気送入管７より圧
搾空気を送り込み前記チユーブ状溶融体３を冷却
マンドレル４の外径に等しいか、それより僅かに
大きい径に膨張させ、その内面を冷却マンドレル
４の表面に接触摺動せしめると同時にその外面を
オーバーフロー管１１よりオーバーフローするこ
とによつて所定の液位に保持された上下動可能な
外部冷却液槽１０中の冷却マンドレルの出口の冷
媒温度以下の冷却液体１２に晒して冷却し下方に
導く。上記冷却マンドレル４の内部はリングダイ
１を貫通する冷却液供給管５及び冷却液排出管６
を有し常時冷媒により（）式に示される冷媒温
度T1，T2に調節されている。次いで冷却マンド
レル４を離れたチユーブ状物はその内部に冷却マ
ンドレル下部に設けられた圧搾空気吹出管８より
圧搾空気を吹出し外部冷却液槽の冷却液体により
潰されないように保たれながらさらに下方に導か
れニツプロール９を経て引取られる。この際得よ
うとする未延伸成形物の厚み（Ｘ）より（）式
を満足するように冷却マンドレルの入口及び出口
における冷媒温度及びチユーブの引取速度を調整
し必要とする温度勾配因子（Ｙ）を設定する。未
延伸成形物の厚み（Ｘ）と温度勾配因子（Ｙ）と
の関係を第２図に示す。第２図中斜線部分が
（）式を満す領域である。
上述した如き方法例によつて得られるチユーブ
状ポリプロピレン未延伸成形物の外側の表層部に
はβ型結晶が特定量発生する。
次にかかるポリプロピレン未延伸成形物に２軸
延伸処理を施すわけであるが、延伸方法としては
フラツト法同時又は逐次２軸延伸法あるいは管状
２軸延伸法を適宜用いることができる。本発明に
おいては上述した如き特定の方法によつて得られ
るβ型結晶を表層部に有するポリプロピレン未延
伸成形物に２軸延伸処理を施すことによつてβ型
結晶からα型結晶への転化の結果体積収縮が生じ
上述した如き特異の粗面構造を有するフイルムと
することができる。
本発明を実施する際における延伸開始点におけ
る延伸温度としてはポリプロピレンのβ型結晶の
融点からα型結晶の融点の範囲の温度、すなわち
145〜176℃なる範囲の温度であることが必須条件
である。ここで延伸開始点とは延伸工程において
未延伸成形物の厚みの減少が実質的に開始される
箇所を意味するものであり、フラツト法同時２軸
延伸法においては左右の相対するクリツプ間距離
が増大し始める箇所であり、フラツト法逐次２軸
延伸法においては縦延伸部においてフイルム厚み
が減少し始める部分である。また管状２軸延伸法
においては延伸タワーヒーター内を通過するチユ
ーブの径が増大し始める部分がこれに相応するも
のである。延伸開始点における延伸温度が本発明
の温度範囲をいずれも外れる場合には本発明の目
的とする電気物品用ポリプロピレンフイルムとす
ることができない。
さらに本発明の実施において２軸延伸する際の
一方向の延伸倍率は８倍未満であることが必須要
件である。一方向の延伸倍率が８倍以上では本発
明の目的とする特異な粗面構造を有するフイルム
とすることができなくなる。また一方向の延伸倍
率の下限には実質的にはネツキング現象により規
制される。ネツキングを終了させるに必要な延伸
倍率は延伸温度等により異なつてくるが、一般に
は一方向につき３倍から６倍の延伸が必要であ
る。
本発明の実施に際しては上記２軸延伸処理の後
に緊張熱処理、緩和熱処理等の通常の熱処理を施
すことにより熱寸法安定性良好なフイルムとする
ことができる。
本発明の目的とする電気物品用ポリプロピレン
フイルムは上述した如き条件を満足する方法によ
つて初めて得られるものであり、いずれか欠ける
条件のもとでは本発明の目的を達成することがで
きない。
本発明の製法によつて得られるフイルムはその
表面に主として繊維状組織が重なり絡み合つて構
成された周縁盛り上り部を有するクレーター状凹
凸構造及びこのクレーター状凹凸構造の内側及
び／又は外側に分布した襞状繊維状構造とから構
成される特異な粗面構造が形成されており、かか
るクレーター状凹凸構造は主としてクレーター状
凹凸構造の直径が0.02〜0.2mmの範囲である大き
なクレーター状凹凸構造とクレーター状凹凸構造
の直径が0.002mm以上0.2mm未満の範囲である小さ
なクレーター状凹凸構造とに分類される。これら
大小のクレーター状凹凸構造は上述した如き製法
に際して種々の条件をコントロールすることによ
つて夫々単独のみで分布している第１ケース、
夫々共存して分布している第２ケース、さらには
小さなクレーター状凹凸構造が大きなクレーター
状凹凸構造の内側に分布している第３ケース、第
１ケースと第３ケースの組合せからなる第４ケー
ス、第２ケースと第３ケースの組合せからなる第
５ケースなど種々の分布状態のケースをとりう
る。また本発明の製法によつて得られるフイルム
の表面には上記大小のクレーター状凹凸構造の内
側及び／又は外側に襞状繊維状構造が分布してお
り、これらクレーター状凹凸構造と襞状繊維状構
造とが共存して高密度に分布しているため絶縁油
の含浸特性に優れ、しかも長期間の使用によつて
も特異な粗面構造のへたりがなく性能の経時的低
下が殆んど起らない特徴を有する。また上述した
如き製法によつて得られるフイルムの表面に形成
されるクレーター状凹凸構造はその製造条件によ
るが上記大小のクレーター状凹凸構造とが共存
し、しかも大きなクレーター状凹凸構造が2500
ケ／cm2以上発現している場合、さらには該小さな
クレーター状凹凸構造が該大きなクレーター状凹
凸構造の内側に５個以上発現している場合に最も
優れた特性を発揮するため非常に好ましいものと
なる。さらに本発明の製法によつて得られるフイ
ルムはその表面粗度が５％以上を有し、該表面粗
度は上記クレーター状凹凸構造の凹凸の度合と密
接な関係にあり、しかも絶縁油の含浸性及び電気
的諸特性の経時的低下防止と密接な関係にある。
ここで表面粗度とはフイルムを100mm×200mmのサ
イズに切り取つたものを５枚重ね、これを粗面側
を内側になるように折り曲げて10枚重ねとしたも
のをマイクロメーターにて測定した厚みをμM、
上記サイズに切り取つた５枚を重量測定し、ポリ
プロピレンの密度0.905ｇ/cm3で除して算出した所
謂重量法にて算出した厚みをμWとすると次式で
求めたものである。
表面粗度＝μM−μW／μW×100（％）
本発明の製法によつて得られる電気物品用ポリ
プロピレンフイルムは機械的性質に優れ、内部構
造が極めて緻密で気密性に富み、しかもその表面
は極めて高密度に分布した粗面構造を有しており
良好な絶縁油含浸性を示すと共に長期間の使用に
おいても優れた電気的特性を保持することができ
電気物品用として優れた特性を発揮する。
以下実施例により本発明を具体的に説明する。
実施例中メルトインデツクス（以後M.I.と略す）
は荷重2160ｇ、温度230℃、プランジヤー直径
9.5φmm、オリフイス直径2φmmでの10分間におけ
る吐出重量である。I.I.は前述した方法によるア
イソタクテイシテイ値である。直流絶縁破壊電圧
（以後BDVと略す）はJIS C2318に準じた方法に
より50点測定を行なつた。またコロナ発生電圧
（以後CSVと略す）は同調式コロナ検出装置で測
定した。
実施例 １
M.I.2.5、I.I.97％の結晶性ポリプロピレンをダ
イ径150mm、リツプ間隙0.5mmのリングダイより第
１表に示す種々の押出温度にて溶融押出してチユ
ーブ状溶融体とした。引続き該溶融体の内面を該
リングダイ直下５mmのところに設置され、その内
部には水を循環させ第１表に示す温度にコントロ
ールされた実効長65cmの冷却マンドレルを用いて
第１表に示す条件により種々の厚みのチユーブ状
未延伸成形物を得た。なおチユーブの外面は30℃
の空気雰囲気に晒した。しかる後かかる未延伸成
形物を150℃にコントロールした赤外線ヒーター
で加熱し、第１表に示す延伸倍率で管状同時２軸
延伸し、次いで各方向に９％の制限収縮下で145
℃で熱処理し第１表に示す種々の厚さを有する２
軸延伸ポリプロピレンフイルムを得た。得られた
延伸フイルムの片側の表面には繊維状組織が重な
り絡み合つて構成された種々の直径を有する大き
なクレーター状凹凸構造、小さなクレーター状凹
凸構造及び襞状繊維状構造が存在していた。これ
らの分布状態及び表面粗度の測定した結果を第２
表に示す。なお小さなクレーター状凹凸構造は大
きなクレーター状凹凸構造の内側に分布してい
た。
The present invention relates to a method for producing a polypropylene film for electrical articles that exhibits excellent insulating oil impregnation properties and electrical properties that can be used in oil-immersed electrical articles such as electric cables, capacitors, and transformers. Biaxially oriented polypropylene film has extremely good dielectric strength and dielectric properties compared to conventionally used insulating paper, so it has recently been used in place of insulating paper to make electrical cables, capacitors, transformers smaller, lighter, and more durable. It has come to be used in various electrical products that require it. Particularly in the case of capacitors, there is a strong tendency to reduce the amount of insulating paper used and increase the proportion of polypropylene film as much as possible from the viewpoint of potential gradient, dielectric constant, dielectric strength, etc. By the way, when increasing the ratio of this polypropylene film, especially when not using insulating paper in combination, the conventional biaxially stretched polypropylene film has a smooth surface, so the film surfaces can be used together or between the film surface and a foil electrode such as aluminum foil. Since the surface is completely sealed, air or moisture trapped inside the capacitor element is thoroughly removed.
In addition, it is extremely difficult to completely impregnate insulating oil between the film surface and the foil-like electrode layer, so corona generation voltage, corona erasing voltage, and dielectric breakdown voltage are likely to decrease due to unimpregnated areas of insulating oil. As a result, it has the disadvantage that it is prone to premature destruction and cannot be manufactured into a product with sufficient electrical characteristics. In the field of film capacitors, for example, in the field of film capacitors, methods to reduce such defects include, in addition to conventional composite dielectrics that use insulating paper, embossing polypropylene films to roughen the film surface by roughening it. A method has been proposed for improving the impregnability of insulating oil by this, but such a method has the disadvantage that the film properties tend to deteriorate and the impregnation of oil into the recesses conversely decreases. There is also a method of blending polypropylene with other polymers to form a film and subjecting it to a stretching process to roughen the surface, but depending on the type of polymer blended, the electrical properties may deteriorate significantly.
It has the disadvantage that it is not possible to obtain a product with sufficiently satisfactory impregnating properties with insulating oil. Furthermore, a method has been proposed in which a network structure is developed on the surface of the film by stretching an unstretched film containing crystals of different types, but the film produced by this method has excellent insulating oil impregnation properties, but has poor overall performance. The electrical characteristics are still not fully satisfactory. In other words, if the impregnated structure on the film surface is made small and deep to ensure the amount of insulating oil impregnated with a simple mesh structure, these structures will deteriorate with use, and even if the initial characteristics are good, the performance will deteriorate over time. So-called V-T decreases
There are some aspects in which favorable results are not necessarily obtained in terms of characteristics. In view of the current situation, the present inventors conducted intensive studies to obtain a polypropylene film for electrical articles having excellent dielectric properties and easy impregnation with insulating oil. The inner surface of the tube-shaped melt obtained by melt extrusion molding is slid onto a cooling mandrel so that the temperature gradient factor is higher than a specific value, and the outer surface of the melt is exposed to a cooling medium at a specific temperature. By biaxially stretching the obtained unstretched polypropylene molded product under specific conditions, it is made up of a crater-like uneven structure and a fold-like fibrous structure, which has a peripheral raised portion mainly composed of overlapping and intertwined fibrous structures. The present inventors have found that a film having a highly densely distributed rough surface structure on the film surface and a surface roughness of 5% or more has been obtained, and that such a film is suitable for the above-mentioned purpose, and has thus arrived at the present invention. That is, the present invention melt-extrudes crystalline polypropylene without adding a β-type crystallization nucleating agent through a ring die at a temperature range of 210 to 250°C to form a tube-shaped melt, and then the inner surface of the tube-shaped melt is While contacting and sliding the tube on a cooling mandrel so that the relationship between the temperature gradient factor (Y) defined by the formula and the thickness (X) of the resulting tube-shaped unstretched product satisfies the following formula (), A polypropylene unstretched product containing no β-type crystallization nucleating agent obtained by exposing the outer surface of a molten body to a cooling medium of T 2 °C or less, cooling it, and taking it off is stretched at a stretching temperature of 145 to 176 °C at the stretching start point. This is a method for producing a polypropylene film for electrical articles, characterized in that biaxial stretching is carried out under conditions such that the stretching ratio in one direction is less than 8 times. Y = (T 2 - T 1 ) x R/L...() Y>4400/X...() However, in the formulas () and (), Y: Temperature gradient factor (°C/sec) T 1 : Cooling mandrel inlet T2 : Refrigerant temperature at the exit of the cooling mandrel (°C) R: Tube take-up speed (cm/sec) L: Effective length of the cooling mandrel (cm) X: Thickness of the unstretched product (μ ) The crystalline polypropylene used in carrying out the present invention includes not only a propylene homopolymer but also a copolymer with a small amount of other α-olefin. It is an isotactic polypropylene with a residue of 90% or more, and its degree of polymerization may be any degree as long as it can be melt-molded, but those with a melt index of 0.5 to 20 are preferred.
In addition, when a special β-type crystallization nucleating agent such as quinacridonequinone, substituted quinacridonequinone, or a metal chelate compound thereof is added to polypropylene, the crystallization nucleating agent or crystallization nucleating agent contained in the film obtained is used. Since fine vacuoles generated inside the film as a result of this influence deteriorate the properties of the film for electrical articles of the present invention, the crystalline polypropylene used in the practice of the present invention does not contain a special β-type crystallization nucleating agent. It is necessary to use one that does not have a The first feature of the film manufacturing method of the present invention is that when manufacturing an unstretched polypropylene product, β
A tube-shaped melt is formed by melt-extruding crystalline polypropylene at a specific temperature range, i.e., 210-250°C, preferably 210-245°C, without adding a crystallization nucleating agent, and this melt is β-type crystals are developed on the outer surface layer of the unstretched molded product by sliding it on the cooling mandrel while applying a specific temperature gradient depending on the thickness of the unstretched molded product to be obtained. This is the point. That is, the overall relationship between the mandrel cooling conditions when using a cooling mandrel, the thickness of an unstretched molded product, and the development of β-type crystals was investigated. The second feature is that the above-mentioned unique rough surface structure is formed on the surface of the film by biaxially stretching the unstretched product having β-type crystals in the surface layer under specific stretching conditions. be. In carrying out the present invention, crystalline polypropylene is melt-extruded through a ring die at a temperature range of 210 to 250°C, preferably 210 to 245°C, to form a tube-shaped melt. This melt extrusion temperature has a strong relationship with the formation of β-type crystal nuclei, and it is assumed that β-type crystal nuclei are generated only after melt extrusion within the above temperature range. Even if the molten material is molded to satisfy the conditions of the above formulas () and (), a preferable product cannot be obtained. Next, the inner surface of the tube-shaped melt obtained by melt extrusion in the above temperature range is brought into contact with and slid on a cooling mandrel, and the outer surface of the tube-shaped melt is exposed to a cooling medium at a specific temperature or lower and taken out to form a tube. The polypropylene unstretched molded product is made by the temperature gradient factor (Y) shown by the above formula ( Various conditions such as cooling conditions of the cooling mandrel, tube take-up speed conditions, and thickness conditions of the unstretched molded product are controlled so that the relationship between Must. Here, the temperature gradient factor (Y) indicates the number of temperature rises per second that the tube-shaped melt undergoes in the drawing direction, and is the amount of β-type crystals that appear on the outer surface layer of the tube-shaped unstretched product. It is closely related to size and distribution. Furthermore, the conditions expressed by the formula () are a region in which sufficient β-type crystals are expressed to obtain a film with a surface roughness of 5% or more,
It is an unprecedented breakthrough that it has become easy to uniquely set the required temperature gradient factor (Y) depending on the thickness (X) of the unstretched product to be obtained. This is a major feature. The cooling mandrel used in carrying out the present invention is a cylindrical object, and its material can be general metal, ceramic, glass, carbon, or polymeric substances. Or it can be made into a woven fabric. The inside of the cooling mandrel has a refrigerant supply pipe and a discharge pipe in order to achieve the above-mentioned temperature gradient factor, and a refrigerant such as air or water is suitably used as the refrigerant. The effective length of the cooling mandrel indicates the length from the position where the inner surfaces of the tube-shaped molten material actually start to come into contact with each other to the position where they separate when they slide into contact. Furthermore, when carrying out the present invention, a water cooling method, an air cooling method, or any other cooling method may be optionally used as a method for cooling the outer surface of the tube-shaped melt by exposing it to a cooling medium having a temperature lower than the refrigerant temperature (T 2 ) at the outlet of the cooling mandrel. Can be done. When the outer surface of the molten body is exposed to a cooling medium at a temperature exceeding T 2 and cooled, it becomes difficult to provide an effective temperature gradient factor, and ultimately the film for electrical articles having the unique rough surface structure of the present invention This is not desirable because it will not be possible to An example of an embodiment for producing an unstretched polypropylene molded product according to the present invention will be explained based on the drawings, but the present invention is not necessarily limited thereto. First, feed the crystalline polypropylene to the extruder.
A tube-shaped melt 3 is obtained by melt extruding through the annular slit 2 of the ring die 1 shown in FIG. 1 at a temperature in the range of 210 to 250°C. Next, compressed air is sent through the compressed air supply pipe 7 to expand the tube-shaped melt 3 to a diameter that is equal to or slightly larger than the outer diameter of the cooling mandrel 4, and its inner surface is brought into contact with the surface of the cooling mandrel 4. At the same time as the cooling mandrel is moved, its outer surface is exposed to the cooling liquid 12 at a temperature lower than the refrigerant temperature at the outlet of the cooling mandrel in the vertically movable external cooling liquid tank 10 which is maintained at a predetermined liquid level by overflowing from the overflow pipe 11. cool it down and guide it downward. Inside the cooling mandrel 4 is a cooling liquid supply pipe 5 and a cooling liquid discharge pipe 6 passing through the ring die 1.
The refrigerant temperature is constantly adjusted by the refrigerant to T 1 and T 2 shown in equation (2). Next, compressed air is blown into the tube-shaped object that has left the cooling mandrel 4 from a compressed air blow-off pipe 8 provided at the lower part of the cooling mandrel, and is guided further downward while being kept from being crushed by the cooling liquid in the external cooling liquid tank. He was taken over via Nitprol 9. At this time, the refrigerant temperature at the inlet and outlet of the cooling mandrel and the tube take-up speed are adjusted to satisfy the formula () from the thickness (X) of the unstretched product to be obtained, and the necessary temperature gradient factor (Y) is determined. Set. FIG. 2 shows the relationship between the thickness (X) of the unstretched molded product and the temperature gradient factor (Y). The shaded area in FIG. 2 is the area that satisfies the equation (). A specific amount of β type crystals is generated in the outer surface layer of the tubular unstretched polypropylene product obtained by the method described above. Next, the unstretched polypropylene molded product is subjected to biaxial stretching treatment, and as the stretching method, a flat method, simultaneous or sequential biaxial stretching method, or tubular biaxial stretching method can be used as appropriate. In the present invention, the conversion from β-type crystals to α-type crystals is achieved by biaxially stretching an unstretched polypropylene product having β-type crystals in the surface layer obtained by the above-mentioned specific method. As a result, volume shrinkage occurs and a film having the above-mentioned unique rough surface structure can be obtained. When carrying out the present invention, the stretching temperature at the starting point of stretching is a temperature in the range from the melting point of β-type crystals of polypropylene to the melting point of α-type crystals, i.e.
A temperature in the range of 145-176°C is essential. The stretching start point here means the point where the thickness of the unstretched molded product substantially starts to decrease in the stretching process, and in the flat simultaneous biaxial stretching method, the distance between the left and right opposing clips is This is the part where the film thickness starts to increase, and in the flat sequential biaxial stretching method, this is the part where the film thickness starts to decrease in the longitudinal stretching part. In the tubular biaxial stretching method, this corresponds to the portion where the diameter of the tube passing through the stretching tower heater begins to increase. If the stretching temperature at the starting point of stretching is outside the temperature range of the present invention, the polypropylene film for electrical articles that is the object of the present invention cannot be obtained. Furthermore, in carrying out the present invention, it is essential that the stretching ratio in one direction during biaxial stretching is less than 8 times. If the stretching ratio in one direction is 8 times or more, the film cannot have the unique rough surface structure that is the object of the present invention. Further, the lower limit of the stretching ratio in one direction is substantially regulated by the netting phenomenon. The stretching ratio required to complete the netting varies depending on the stretching temperature, etc., but generally it is necessary to stretch 3 to 6 times in one direction. In carrying out the present invention, a film with good thermal dimensional stability can be obtained by subjecting the film to a conventional heat treatment such as tension heat treatment or relaxation heat treatment after the biaxial stretching process. The polypropylene film for electrical articles, which is the object of the present invention, can only be obtained by a method that satisfies the above-mentioned conditions, and the object of the present invention cannot be achieved if any of the conditions are lacking. The film obtained by the production method of the present invention has a crater-like uneven structure on its surface, which has a peripheral raised part mainly composed of overlapping and intertwined fibrous structures, and distribution inside and/or outside of this crater-like uneven structure. A unique rough surface structure is formed which is composed of a fold-like fibrous structure, and this crater-like uneven structure is mainly composed of a large crater-like uneven structure whose diameter is in the range of 0.02 to 0.2 mm. It is classified as a small crater-like uneven structure in which the diameter of the crater-like uneven structure is in the range of 0.002 mm or more and less than 0.2 mm. In the first case, these large and small crater-like uneven structures are individually distributed by controlling various conditions during the manufacturing method as described above.
A second case in which they are distributed together, a third case in which a small crater-like uneven structure is distributed inside a large crater-like uneven structure, and a fourth case that is a combination of the first case and the third case. , a fifth case consisting of a combination of the second case and the third case, and various other distribution states can be taken. In addition, on the surface of the film obtained by the production method of the present invention, pleated fibrous structures are distributed inside and/or outside of the above-mentioned large and small crater-like uneven structures, and these crater-like uneven structures and pleated fibrous structures are distributed. Because it coexists with the structure and is densely distributed, it has excellent impregnating properties with insulating oil, and even after long-term use, the unique rough surface structure does not deteriorate, and there is almost no deterioration in performance over time. It has the characteristic that it does not occur. Furthermore, the crater-like uneven structure formed on the surface of the film obtained by the above-mentioned manufacturing method depends on the manufacturing conditions, but the above-mentioned large and small crater-like uneven structures coexist, and the large crater-like uneven structure is 2500
It is very preferable that the most excellent properties are exhibited when 5 or more of the small crater-like uneven structures are formed inside the large crater-like uneven structure . becomes. Furthermore, the film obtained by the production method of the present invention has a surface roughness of 5% or more, and the surface roughness is closely related to the degree of unevenness of the crater-like uneven structure, and moreover, the film is impregnated with insulating oil. This is closely related to preventing the deterioration of physical and electrical properties over time.
Here, surface roughness is the thickness measured with a micrometer by stacking 5 sheets of film cut into 100 mm x 200 mm size, folding them so that the rough side is inward, and stacking 10 sheets. μM ,
Five pieces cut to the above size were weighed and divided by the density of polypropylene, 0.905 g/cm 3 . The thickness was calculated using the so-called gravimetric method, and μW was calculated using the following formula. Surface roughness = μ M − μ W / μ W ×100 (%) The polypropylene film for electrical articles obtained by the production method of the present invention has excellent mechanical properties, an extremely dense internal structure, and is highly airtight. Its surface has a rough surface structure with extremely high density distribution, exhibits good insulating oil impregnation properties, and maintains excellent electrical properties even after long-term use, making it an excellent property for electrical products. demonstrate. The present invention will be specifically explained below using Examples.
Melt index in Examples (hereinafter abbreviated as MI)
load 2160g, temperature 230℃, plunger diameter
This is the discharge weight in 10 minutes with an orifice diameter of 9.5φmm and an orifice diameter of 2φmm. II is the isotacticity value obtained by the method described above. Direct current breakdown voltage (hereinafter abbreviated as BDV) was measured at 50 points using a method based on JIS C2318. In addition, the corona generation voltage (hereinafter abbreviated as CSV) was measured using a tunable corona detection device. Example 1 Crystalline polypropylene having an MI of 2.5 and an II of 97% was melt-extruded through a ring die with a die diameter of 150 mm and a lip gap of 0.5 mm at various extrusion temperatures shown in Table 1 to obtain a tube-shaped melt. Subsequently, the inner surface of the melt was placed 5 mm directly below the ring die using a cooling mandrel with an effective length of 65 cm, which was controlled to the temperature shown in Table 1 by circulating water inside the mandrel, as shown in Table 1. Tube-shaped unstretched molded products with various thicknesses were obtained depending on the conditions. The outside surface of the tube is 30℃.
exposed to the air atmosphere. Thereafter, the unstretched molded product was heated with an infrared heater controlled at 150°C, and simultaneously biaxially stretched into a tubular shape at the stretching ratio shown in Table 1.
2 with various thicknesses shown in Table 1 after heat treatment at ℃.
An axially stretched polypropylene film was obtained. On one surface of the obtained stretched film, there were a large crater-like uneven structure of various diameters, a small crater-like uneven structure, and a pleated fibrous structure, which were composed of overlapping and intertwined fibrous structures. The results of measuring these distribution states and surface roughness are
Shown in the table. The small crater-like uneven structure was distributed inside the large crater-like uneven structure.
【表】【table】
【表】
実施例 ２
M.I.3.5、I.I.97％の結晶性ポリプロピレンをダ
イ径160mm、リツプ間隙1.5mmのリングダイより押
出温度240℃にて溶融押出してチユーブ状溶融体
とした。引続き該溶融体の内面を該リングダイ直
下20cmのところに設置された実効長65cmの冷却マ
ンドレルを用い、その内部に水を循環させること
により第３表に示す温度条件にコントロールされ
た冷却マンドレル上に接触摺動させると共にその
外面を第３表に示す温度にコントロールされた外
部冷却液槽中の水に晒し冷却しながら第３表に示
す種々の引取速度にて下方に引取り厚さが夫々
437μなるチユーブ状未延伸成形物を得た。しか
る後これら未延伸成形物を160℃にコントロール
した赤外線ヒーターで加熱し、第３表に示す延伸
倍率で管状同時２軸延伸し、次いで各方向に９％
の制限収縮下で145℃で熱処理し厚さが夫々15μ
なる２軸延伸ポリプロピレンフイルムを得た。こ
れら得られた延伸フイルムの片側の表面には繊維
状組織が重なり絡み合つて構成された種々の直径
を有する大小のクレーター状凹凸構造及び襞状繊
維状構造が存在していた。これらの分布状態及び
表面粗度の測定した結果を第４表に示す。なお小
さなクレーター状凹凸構造は大きなクレーター状
凹凸構造の内側に分布していた。
次にこれら得られた延伸フイルムを夫々用い、
6μのアルミニウム電極箔１枚／フイルム２枚／
13μの絶縁紙１枚の構成で2.4KVAC、0.6μFのコ
ンデンサーを作成し、CSV、BDVを測定した。
これらの結果を第５表に示す。[Table] Example 2 Crystalline polypropylene having an MI of 3.5 and an II of 97% was melt-extruded through a ring die with a die diameter of 160 mm and a lip gap of 1.5 mm at an extrusion temperature of 240°C to obtain a tube-shaped melt. Subsequently, the inner surface of the molten material was cooled on a cooling mandrel with an effective length of 65 cm installed 20 cm directly below the ring die, and the temperature conditions shown in Table 3 were controlled by circulating water inside the cooling mandrel. At the same time, the outer surface was exposed to water in an external cooling liquid tank whose temperature was controlled as shown in Table 3, and while cooling, the material was drawn downward at various drawing speeds shown in Table 3, so that the thickness of the material was reduced, respectively.
A tubular unstretched product having a diameter of 437 μm was obtained. Thereafter, these unstretched molded products were heated with an infrared heater controlled at 160°C, and simultaneously biaxially stretched into a tubular shape at the stretching ratio shown in Table 3, and then 9% in each direction.
Heat treated at 145℃ under limited shrinkage to a thickness of 15μ each
A biaxially stretched polypropylene film was obtained. On one surface of each of the obtained stretched films, there existed a crater-like uneven structure of various sizes and a pleated fibrous structure, which were composed of overlapping and intertwined fibrous structures and having various diameters. Table 4 shows the results of measuring these distribution states and surface roughness. The small crater-like uneven structure was distributed inside the large crater-like uneven structure. Next, using each of these obtained stretched films,
1 piece of 6μ aluminum electrode foil / 2 pieces of film /
A 2.4KVAC, 0.6μF capacitor was created using one sheet of 13μ insulating paper, and CSV and BDV were measured.
These results are shown in Table 5.
【表】【table】
【表】【table】
第１図は本発明の実施において結晶性ポリプロ
ピレンを溶融押出してチユーブ状物にする際の溶
融押出成形装置の実施態様例を示す。
１：リングダイス、２：環状スリツト、３：チ
ユーブ状溶融体、４：冷却マンドレル、５：冷却
液供給管、６：冷却液排出管、７：圧搾空気送入
管、８：圧搾空気吹出管、９：ニツプロール、１
０：外部冷却液槽、１１：オーバーフロー管、１
２：冷却液体。
第２図はチユーブ状未延伸成形物の厚み（Ｘ）
と温度勾配因子（Ｙ）との関係を示す。
FIG. 1 shows an embodiment of a melt extrusion molding apparatus for melt extruding crystalline polypropylene to form a tube-shaped product in the practice of the present invention. 1: Ring die, 2: Annular slit, 3: Tubular melt, 4: Cooling mandrel, 5: Coolant supply pipe, 6: Coolant discharge pipe, 7: Compressed air supply pipe, 8: Compressed air blow-off pipe , 9: Nituprole, 1
0: External cooling liquid tank, 11: Overflow pipe, 1
2: Cooling liquid. Figure 2 shows the thickness (X) of the tube-shaped unstretched product.
and the temperature gradient factor (Y).
Claims (1)
ピレンを210〜250℃の温度範囲にてリングダイよ
り溶融押出してチユーブ状溶融体とし、引続き該
チユーブ状溶融体の内面を下記（）式で定義さ
れる温度勾配因子（Ｙ）と得られるチユーブ状未
延伸成形物の厚み（Ｘ）との関係が下記（）式
を満足するように冷却マンドレル上に接触摺動さ
せると共に、該チユーブ状溶融体の外面をT2℃
以下の冷却媒体に晒し冷却し引取ることにより得
られるβ型結晶化核剤を含有しないポリプロピレ
ン未延伸成形物を延伸開始点における延伸温度が
145〜176℃、一方向の延伸倍率が８倍未満なる条
件で２軸延伸することを特徴とする電気物品用ポ
リプロピレンフイルムの製造方法。 Ｙ＝（T2−T1）×Ｒ／Ｌ ……（） Ｙ＞4400／Ｘ ……（） 但し （）、（）式中 Ｙ：温度勾配因子（℃／秒） T1：冷却マンドレル入口の冷媒温度（℃） T2：冷却マンドレル出口の冷媒温度（℃） Ｒ：チユーブの引取速度（cm／秒） Ｌ：冷却マンドレルの実効長（cm） Ｘ：未延伸成形物の厚さ（μ）[Claims] 1 Crystalline polypropylene to which no β-type crystallization nucleating agent is added is melt-extruded from a ring die at a temperature range of 210 to 250°C to form a tube-shaped melt, and then the inner surface of the tube-shaped melt is While contacting and sliding on a cooling mandrel so that the relationship between the temperature gradient factor (Y) defined by the following formula () and the thickness (X) of the obtained tubular unstretched product satisfies the following formula (), , the outer surface of the tube-shaped melt is heated to T 2 °C
The stretching temperature at the stretching start point is
A method for producing a polypropylene film for electrical articles, which comprises biaxially stretching at 145 to 176°C and a stretching ratio of less than 8 times in one direction. Y = (T 2 - T 1 ) x R/L...() Y>4400/X...() However, in the formulas () and (), Y: Temperature gradient factor (°C/sec) T 1 : Cooling mandrel inlet T2 : Refrigerant temperature at the exit of the cooling mandrel (°C) R: Tube take-up speed (cm/sec) L: Effective length of the cooling mandrel (cm) X: Thickness of the unstretched product (μ )
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2837380A JPS56123828A (en) | 1980-03-06 | 1980-03-06 | Manufacturing method for polypropylene film for electrical appliances |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2837380A JPS56123828A (en) | 1980-03-06 | 1980-03-06 | Manufacturing method for polypropylene film for electrical appliances |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS56123828A JPS56123828A (en) | 1981-09-29 |
| JPS6344534B2 true JPS6344534B2 (en) | 1988-09-06 |
Family
ID=12246818
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2837380A Granted JPS56123828A (en) | 1980-03-06 | 1980-03-06 | Manufacturing method for polypropylene film for electrical appliances |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS56123828A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5163500A (en) * | 1974-11-29 | 1976-06-01 | Mitsubishi Rayon Co | |
| JPS5235272A (en) * | 1975-09-16 | 1977-03-17 | Mitsubishi Rayon Co | Method of manufacturing translucent polypropylene elongation film |
| JPS52139176A (en) * | 1976-05-17 | 1977-11-19 | Mitsubishi Rayon Co | Method of manufacturing poly propylene films for electric use |
-
1980
- 1980-03-06 JP JP2837380A patent/JPS56123828A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5163500A (en) * | 1974-11-29 | 1976-06-01 | Mitsubishi Rayon Co | |
| JPS5235272A (en) * | 1975-09-16 | 1977-03-17 | Mitsubishi Rayon Co | Method of manufacturing translucent polypropylene elongation film |
| JPS52139176A (en) * | 1976-05-17 | 1977-11-19 | Mitsubishi Rayon Co | Method of manufacturing poly propylene films for electric use |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS56123828A (en) | 1981-09-29 |
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