JP3731262B2

JP3731262B2 - Production method of thermoplastic resin film

Info

Publication number: JP3731262B2
Application number: JP26104996A
Authority: JP
Inventors: 司大嶋; 豊松村
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 1996-10-01
Filing date: 1996-10-01
Publication date: 2006-01-05
Anticipated expiration: 2016-10-01
Also published as: JPH10100226A

Description

【０００１】
【発明の属する技術分野】
本発明は熱可塑性樹脂フィルムの製法に関し、特に回転式冷却ロール上に熱可塑性樹脂をフィルム状に溶融押出しし、これを上記冷却ロールに密着させて固化させながら引き取るに当たり、上記冷却ロール上に溶融押出しされるフィルムの両側縁で生じる振動を防止し、該振動に起因するフィルム厚さの変動を抑えて厚さの均一なフィルムを得る方法に関するものである。
【０００２】
【従来の技術】
ポリエチレンやポリプロピレン等のポリオレフィンやポリエステル、ポリアミド等の熱可塑性樹脂からなるフィルムを製造する方法として最も一般的に採用されているのは、加熱溶融した熱可塑性樹脂をスリット状のノズルから、高速で回転する冷却ロール上へ押し出し、該冷却ロールに密着させて冷却・固化させながら引き取る方法である。このとき、得られるフィルムの性能や均質性を高めるには、溶融押し出しされる熱可塑性樹脂が、高速で回転する冷却ロール表面に接触して冷却される過程で、該ロールとフィルムの間へ空気が巻き込まれるのを防止し、フィルム状で押し出される熱可塑性樹脂をうまく冷却ロールに密着させることである。
【０００３】
そのための手段として汎用されているのは、強制空気押付法、静電押付法および真空押付法である。このうち真空押付法は、例えば特公昭６３−５７２２２号公報に記載されている様に、溶融押出しされた熱可塑性樹脂フィルムが冷却ロールと接触し始める接触線（一般に「密着点」と呼ばれているので、以下の説明ではこの表現を採用することがある）の冷却ロール回転方向上流側から吸引し、冷却ロールとフィルムの間に空気が侵入するのを防止する方法であり、最も簡単で効率の良い方法として広く実用化されている。即ち空気押付法や静電押付法では、冷却ロールの高速回転による空気泡の侵入を完全に防止することはできないが、真空押付法では、溶融押出しフィルムの密着点近傍から空気を吸引排気して該ロール表面へ該フィルムを密着させる方法であるから、高速回転条件下においても吸引度を調整することによって空気の侵入を効率よく阻止することができる。
【０００４】
【発明が解決しようとする課題】
ところが本発明者らが種々研究を進めるうち、上記真空押付法には次の様な問題を生じることが明らかとなってきた。即ちこの方法では、空気の吸引によって特にネックイン部から外気がかなりの流量・流速で流入してくるため、該外気の流入によって未固化状態の熱可塑性樹脂フィルムのネックイン部が振動し、該振動によりフィルムの厚さが変動したり変形を起こし、フィルムの均一性や外観が悪くなるのである。そこでこうした問題を回避するため上記特公昭６３−５７２２２号では、真空吸引帯域を第１吸引帯域と第２吸引帯域によって構成し、第１吸引帯域では、冷却ロールと溶融押出フィルムとの接触線の中央部全域から空気を吸引し、第２吸引帯域では、上記接触線の両端部側から空気を吸引する方法を採用している。
【０００５】
ところがこの方法でも、本出願で問題として掲げる上記フィルム両側縁の振動を確実に阻止することはできず、特に冷却ロールの回転速度を高めて生産速度を高めようとすると、フィルム厚さの不均一が顕著に現われてくる。
【０００６】
本発明は上記の様な事情に着目してなされたものであって、その目的は、吸引押付法を採用して熱可塑性樹脂フィルムを製造する際に、吸引によって生じる熱可塑性樹脂フィルム両側縁部の振動を抑え、両側縁部はもとより中央部においても厚みや性状の均一なフィルムを得ることのできる方法を確立しようとするものである。
【０００７】
【課題を解決するための手段】
上記課題を解決することのできた本発明の製法は、回転式冷却ロール上に熱可塑性樹脂をフィルム状に溶融押出しすると共に、上記フィルムが上記冷却ロールに接触し始める接触線における上記冷却ロールの回転方向上流側に近接して設けた主吸引手段によって、該フィルムと冷却ロール間から空気を吸引排除しつつ引き取る熱可塑性樹脂フィルムの製法において、前記接触線の両端側に補助吸引手段を設け、該接触線と略平行で且つ外側方向への誘導排出を行うところに要旨を有している。
【０００８】
本発明を実施するに当たっては、上記補助吸引手段による吸引力が、主吸引手段の吸引力を超えない様に制御することによって、フィルム両側縁部の振動をより効果的に抑えることができ、厚みや性状の非常に均一なフィルムを得ることが可能となる。
【０００９】
【発明の実施の形態】
上記の様に本発明では、真空押付法を採用した熱可塑性樹脂フィルムの製法によって得られる空気の侵入防止効果を有効に活かしつつ、吸引に伴なって生じる外気の侵入によるフィルム両側縁部の振動を阻止する為の手段として、上記吸引押し付けの為の主吸引手段とは別に、溶融押し出しされたフィルムが冷却ロールと接触し始める接触線（即ち「密着点」）の両端側に補助吸引手段を設け、該補助吸引手段によって、上記密着点と略平行向、即ち冷却ロールの回転方向と略直行する方向に吸引するものであり、該補助吸引によって外部からのフィルム−冷却ロール間への空気の侵入量を抑え、ひいてはネックイン部両端部の振動を抑制するものである。その結果として、溶融押出しフィルムはネックイン部の両側縁とも殆んど振動無しの状態で冷却ロールに接触して急冷固化されることになり、フィルムの両側縁部はもとより中央部においても厚さや性状の不均一を起こすことなく、極めて均質性の高いフィルムを確実に得ることが可能となる。
【００１０】
以下、実施例図面を参照しつつ本発明の構成や作用効果を詳細に説明する。
図１は本発明で用いられるフィルム製造装置を例示する概略縦断面説明図、図２は図１を右方向から見た図、図３は、スリット状ノズルからフィルム状で押し出された熱可塑性樹脂が冷却ロールに接触して冷却固化されながら引き取られていく状態を示した平面説明図であり、図中１は冷却ロール、２は熱可塑性樹脂押出装置、３は主吸引手段、４は補助吸引手段を示しており、押出装置２内の加熱溶融された熱可塑性樹脂Ｒは、任意の手段によって加えられる背圧を受けてスリット状ノズル２ａからフィルム状で押し出された後、回転する冷却ロール１に接触して冷却固化し、該冷却ロール１の回転に伴って白抜き矢印方向に引き取られていく。この時、前記スリット２ａからフィルム状で溶融押出しされた熱可塑性樹脂Ｒが冷却ロール１に接触し始める接触線を密着点Ｍとする。
【００１１】
そしてこの密着点Ｍで、フィルム状で押し出される熱可塑性樹脂Ｒと冷却ロール１の間に空気が浸入するのを阻止するため、本発明でも従来技術と同様に、密着点Ｍにおける冷却ロールの回転方向背部側に主吸引手段３を設け、該密着点Ｍにおけるフィルムと冷却ロール間の空気を吸引排気することによって、熱可塑性樹脂フィルムＲを冷却ロール１の表面に密着させる構成としている。なお図１における主吸引手段３は、上記密着点Ｍに指向する面を除いて実質的に封鎖されており、冷却ロール１に面した部分は、たとえばラビリンスパッキン構造等とすることによって隙間を小さくし、密着点Ｍから集中的に吸引できる様に構成されている。
【００１２】
上記の如く密着点Ｍの幅方向全域に主吸引箱３からの吸引力を作用させ、フィルム−冷却ローラ１間の空気を吸引排気して密着させる方法自体は、先に掲げた特公昭６３−５７２２２号等によって既に公知であり、密着性改善の目的は達成される。
【００１３】
ところがこの様な真空密着法を採用した場合、密着点Ｍの中央部はフィルムが冷却ロール１の表面に密着しているため空気が侵入する余地がなく、該密着点Ｍの両端部側の隙間のみから集中的に外気が侵入してくるので、該侵入空気の流れによってネックイン部の両端部が振動し、該振動によって未固化状態の熱可塑性樹脂フィルムの厚みや形状が変動する。その結果、でき上がりフィルム両側縁部の肉厚が不均一になったり変形するといった問題が生じてくる。
【００１４】
本発明では、こうした従来の真空密着法に見られネックイン部の振動を抑止し、フィルム両側縁の肉厚や形状の不均一を解消して均質性の高いフィルムを製造可能にするものであり、具体的には、図示する如く主吸引手段とは別に、密着点Ｍの両端側に補助吸引手段を設け、該密着点Ｍを構成する接触線と略平行方向に、好ましくは主吸引手段３の吸引力を上回らない吸引力で吸引を行なうことによって、上記の様なネックイン部両端部の振動を抑える方法を採用している。
【００１５】
該補助吸引手段４を設けることによって前述の様な振動が抑えられる理由は、次の様に考えられる。即ちネックイン部の両端部が振動を起こす理由は、前述の如く、主吸引手段３からの吸引に伴って、密着点Ｍ両端部側から外気がかなりの流速と流量で侵入してくるからであると考えられる。ところが、図示する如く密着点Ｍの両端部側に補助吸引手段４を設け、該補助吸引手段４から、密着点Ｍを構成する接触線と略平行方向に吸引を行なうと、例えば図４に略示する如く、密着点Ｍの両端部から流入する外気の一部が補助吸引手段４によって外側に誘導排出され、密着点Ｍの両端部を通して内側へ流入する外気の流量が減少し、その結果、外気流入によって生じるネックイン部両端部の振動が抑えられるものと考えられる。
【００１６】
そして本発明者らが種々検討を重ねたところによると、こうした補助吸引手段４による振動防止効果は、該補助吸引手段４による吸引方向を密着点Ｍを構成する接触線の略平行方向に吸引することによって有効に発揮され、該吸引方向がたとえば上記接触線に対して垂直方向では、本発明で意図する様な振動防止効果は得られないことが確認された。その理由は必ずしも明確にされた訳ではないが、単に垂直方向、即ち主吸引手段３の吸引方向と同じ方向に吸引したのでは、密着点Ｍの両側を通して一旦流入した外気の一部を補助吸引手段４によって吸引排気することになり、ネックイン部の両端部を通過する外気流量は実質的に変わらなくなるため、振動防止効果が有効に発揮されなくなるものと思われる。そして上記の様な振動防止効果を有効に発揮させるには、前記接触線に対して平行方向に補助吸引することが最も好ましいが、±１０°程度であれば吸引方向が若干斜め方向であっても、一応満足のいく振動防止効果が発揮されることを確認している。
【００１７】
なお上記補助吸引手段４による吸引力は、主吸引手段３による吸引力を超えない様に制御することが望ましい。しかし、補助吸引手段４による吸引力が強くなりすぎると、該補助吸引手段４によって形成される大きな吸引流がネックイン部で新たに形成されることになり、この吸引流による新たな振動が発生するためと思われる。しかも補助吸引手段４による吸引力が強くなりすぎると、主吸引手段３による吸引力が相対的に小さくなり、密着点Ｍの中央部側で密着不足を生じる恐れも出てくる。
【００１８】
これに対し、補助吸引手段４による吸引力が主吸引手段３の吸引力を超えない様に制御すると、補助吸引手段４による新たな外気流れで振動を起こしたり、密着点Ｍの中央部側で密着不良等の問題を起こすことなく、ネックイン部両端部の振動を効果的に抑えることができ、それに伴ってフィルム両側縁部の厚さや形状の変動を可及的に抑えることが可能となる。こうした補助吸引部４からの補助吸引による振動防止効果をより効果的に発揮させるには、その吸引力を主吸引手段３の吸引力に対して６０〜１００％程度の範囲に制御するのが最も好ましい。
【００１９】
補助吸引手段４を構成する吸引口の形状には一切制限がなく、円形、楕円形、矩形など任意の形状のものを採用できるが、振動防止効果をより有効に発揮させるには、冷却ロールの表面に近接した位置から流入空気の一部を効率よく吸引排気できる様、その下面側を冷却ロールの曲率に応じて局面成形した矩形状のものが最も好ましい。
【００２０】
【実施例】
次に実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更して実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。
【００２１】
内径９０ｍｍの溶融押出機の先端に、内幅２６０ｍｍのスリットを設けたＴダイを接続し、該スリットからナイロン６を溶融押出しし、直径９００ｍｍの回転式冷却ロール上にバキュームチャンバー（主吸引手段）からの吸引力によって密着させながら急冷固化させ、厚み１００μｍのナイロンフィルムを３５ｍｍ／ｍｉｎの速度で引き取った。この時、密着点の両端側に、フィルム巻き取り方向と直行する方向に、吸引口サイズが１０×３０ｍｍの吸引ノズル（補助吸引手段）を設け、バキュームチャンバーから３０ｍ／ｓｅｃで吸引しつつ、吸引ノズルから、０（未吸引）、２０ｍ／ｓｅｃまたは３０ｍ／ｓｅｃの速度で吸引した場合について、フィルム幅方向の厚みの変動率を下記の方法によって測定した。
【００２２】
即ち、急冷固化して巻き取ったナイロンフィルム１０ｍを採取し、夫々につき、図５に示す如く幅方向に７等分した中心位置の各々について平均厚み、最大厚みおよび最小厚みを測定し、下記式によって厚み変動率を求めた。
厚み変動率（％）＝［（最大厚み−最小厚み）／平均厚み］×１００
【００２３】
結果は表１に示す通りであり、吸引ノズルからの吸引を行なわなかった場合（従来例）の厚み変動率は７．５％とかなり大きいのに対し、吸引ノズルから２０ｍ／ｓｅｃの速度で補助吸引を行なうと、厚み変動率を５．５％に減少することができ、またバキュームチャンバーからの吸引量と同じ３０ｍ／ｓｅｃで補助吸引した場合は、厚み変動率を５．１％にまで低減できることが分かる。
【００２４】
【表１】

【００２５】
【発明の効果】
本発明は以上の様に構成されており、真空密着法を採用して熱可塑性樹脂フィルムの製造を行なう際に、従来の主吸引手段とは別に補助吸引手段を設けて密着点の両端部側から侵入してくる外気の一部を該補助吸引手段によって吸引排気することにより、該ネックイン両端部の振動を可及的に防止することができ、該振動に伴って生じていたフィルム両側縁の肉厚や形状の変動を可及的に抑制し、幅方向全域にわたって均質性の高いフィルムを製造し得ることになった。
【図面の簡単な説明】
【図１】本発明を採用したフィルム製造状況を例示する要部断面説明図である。
【図２】図１を右方向から見た概略説明図である。
【図３】密着点からの外気の流入状況を示す概略平面説明図である。
【図４】補助吸引手段からの吸引を併用した時の、密着点両端部の振動抑制効果を説明するための概略斜視説明図である。
【図５】実施例で得たフィルムの厚み変動率測定位置を示す説明図である。
【符号の説明】
１冷却ロール
２溶融押出装置
２ａスリット状ノズル
３主吸引手段
４補助吸引手段
Ｍ密着点[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a thermoplastic resin film, and in particular, melts and extrudes a thermoplastic resin into a film form on a rotating chill roll and draws it while adhering to the chill roll and solidifying it. The present invention relates to a method for preventing a vibration generated at both side edges of an extruded film and obtaining a film having a uniform thickness by suppressing a variation in the film thickness caused by the vibration.
[0002]
[Prior art]
Polyolefins and polyesters such as polyethylene and polypropylene, the most commonly employed as a method for producing a thermoplastic resin or Rana Ru films such as polyamide is a heated and melted thermoplastic resin from a slit-shaped nozzle, high-speed It is a method of extruding onto a rotating chill roll and taking it while closely contacting the chill roll and cooling and solidifying. At this time, in order to improve the performance and homogeneity of the obtained film, the thermoplastic resin to be melt-extruded is cooled in contact with the surface of the cooling roll rotating at high speed, and air is introduced between the roll and the film. Is prevented from being caught, and the thermoplastic resin extruded in the form of a film is well adhered to the cooling roll.
[0003]
For this purpose, the forced air pressing method, electrostatic pressing method and vacuum pressing method are widely used. Among these, the vacuum pressing method is a contact line (generally called “adhesion point”) at which the melt-extruded thermoplastic resin film comes into contact with the cooling roll, as described in, for example, Japanese Patent Publication No. 63-57222. (This expression may be used in the following explanation) This is a method that sucks in from the upstream side of the cooling roll rotation direction and prevents air from entering between the cooling roll and the film. It is widely used as a good method. In other words, the air pressing method and the electrostatic pressing method cannot completely prevent the intrusion of air bubbles due to the high-speed rotation of the cooling roll, but the vacuum pressing method sucks and exhausts air from the vicinity of the contact point of the melt-extruded film. Since the film is brought into close contact with the surface of the roll, air intrusion can be efficiently prevented by adjusting the degree of suction even under high-speed rotation conditions.
[0004]
[Problems to be solved by the invention]
However, as the inventors proceeded with various studies, it has become clear that the following problems occur in the vacuum pressing method. That is, in this method, since the outside air flows in from the neck-in portion at a considerable flow rate / flow velocity due to the suction of air, the neck-in portion of the unsolidified thermoplastic resin film vibrates due to the inflow of the outside air. The thickness of the film fluctuates or deforms due to vibration, and the uniformity and appearance of the film deteriorate. Therefore, in order to avoid such a problem, in the above Japanese Patent Publication No. 63-57222, the vacuum suction zone is constituted by the first suction zone and the second suction zone, and in the first suction zone, the contact line between the cooling roll and the melt-extruded film is reduced. In the second suction zone, air is sucked from the entire central portion, and air is sucked from both end portions of the contact line.
[0005]
However, even with this method, it is not possible to reliably prevent the vibrations on both sides of the film, which are raised as a problem in the present application. Especially, when the production speed is increased by increasing the rotation speed of the cooling roll, the film thickness is uneven. Appears prominently.
[0006]
The present invention has been made paying attention to the circumstances as described above, and the purpose thereof is to employ both sides of the thermoplastic resin film produced by suction when a thermoplastic resin film is produced by employing the suction pressing method. Thus, the present invention intends to establish a method capable of obtaining a film having a uniform thickness and properties not only at both side edges but also at the center.
[0007]
[Means for Solving the Problems]
The manufacturing method of the present invention that has been able to solve the above-described problems is the method of melt-extruding a thermoplastic resin into a film on a rotating cooling roll and rotating the cooling roll at a contact line at which the film starts to contact the cooling roll. In a method for producing a thermoplastic resin film that is drawn off while sucking and removing air from between the film and the cooling roll by the main suction means provided close to the upstream side in the direction, auxiliary suction means are provided on both ends of the contact line, The gist is that the guided discharge is performed substantially parallel to the contact line and outward .
[0008]
In carrying out the present invention, by controlling the suction force by the auxiliary suction means so as not to exceed the suction force of the main suction means, vibrations on both side edges of the film can be more effectively suppressed. It becomes possible to obtain a film with a very uniform property.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As described above, in the present invention, while effectively utilizing the air intrusion prevention effect obtained by the thermoplastic resin film manufacturing method adopting the vacuum pressing method, vibrations on both side edges of the film due to the intrusion of outside air accompanying suction In addition to the main suction means for sucking and pressing, auxiliary sucking means are provided at both ends of a contact line (that is, “contact point”) at which the melt-extruded film starts to come into contact with the cooling roll. The auxiliary suction means sucks in a direction substantially parallel to the contact point, that is, in a direction substantially perpendicular to the rotation direction of the cooling roll, and the auxiliary suction sucks air from the outside between the film and the cooling roll. The amount of intrusion is suppressed, and consequently vibrations at both ends of the neck-in portion are suppressed. As a result, the melt-extruded film is brought into contact with the cooling roll with almost no vibration on both side edges of the neck-in part and is rapidly cooled and solidified. It is possible to reliably obtain a film with extremely high homogeneity without causing unevenness of properties.
[0010]
Hereinafter, the configuration and operational effects of the present invention will be described in detail with reference to the accompanying drawings.
1 is a schematic longitudinal sectional view illustrating a film manufacturing apparatus used in the present invention, FIG. 2 is a view of FIG. 1 viewed from the right direction, and FIG. 3 is a thermoplastic resin extruded in a film form from a slit-like nozzle. FIG. 1 is an explanatory plan view showing a state in which a chill roll is taken out while being cooled and solidified, in which 1 is a cooling roll, 2 is a thermoplastic resin extrusion device, 3 is a main suction means, and 4 is an auxiliary suction. The heat-melted thermoplastic resin R in the extrusion apparatus 2 is subjected to a back pressure applied by an arbitrary means and is extruded in the form of a film from the slit nozzle 2a, and then the cooling roll 1 that rotates. It is cooled and solidified in contact with the sheet, and is drawn in the direction of the white arrow as the cooling roll 1 rotates. At this time, a contact line at which the thermoplastic resin R melt-extruded in a film form from the slit 2 a starts to contact the cooling roll 1 is defined as an adhesion point M.
[0011]
In order to prevent air from entering between the thermoplastic resin R extruded in the form of a film and the cooling roll 1 at the contact point M, the rotation of the cooling roll at the contact point M is also performed in the present invention in the same manner as in the prior art. The main suction means 3 is provided on the direction back side, and the thermoplastic resin film R is brought into close contact with the surface of the cooling roll 1 by sucking and exhausting air between the film and the cooling roll at the contact point M. Note that the main suction means 3 in FIG. 1 is substantially sealed except for the surface directed to the contact point M, and the portion facing the cooling roll 1 has a labyrinth packing structure or the like to reduce the gap. However, it is configured so that it can be intensively sucked from the contact point M.
[0012]
As described above, the method itself of applying the suction force from the main suction box 3 to the entire area in the width direction of the contact point M and sucking and exhausting the air between the film and the cooling roller 1 is described in Japanese Patent Publication No. Sho 63-. No. 57222 etc. are already known, and the purpose of improving adhesion is achieved.
[0013]
However, when such a vacuum contact method is employed, there is no room for air to enter in the central portion of the contact point M because the film is in close contact with the surface of the cooling roll 1, and there is no clearance between the both ends of the contact point M. Since the outside air intensively enters only from the above, both ends of the neck-in portion vibrate due to the flow of the invading air, and the thickness and shape of the unsolidified thermoplastic resin film change due to the vibration. As a result, there arises a problem that the thickness of the both side edges of the finished film becomes uneven or deforms.
[0014]
In the present invention, it is possible to produce a highly homogeneous film by suppressing the vibration of the neck-in portion as seen in such a conventional vacuum contact method, and eliminating unevenness in the thickness and shape of both side edges of the film. Specifically, as shown in the drawing, auxiliary suction means are provided on both ends of the contact point M separately from the main suction means, and preferably in a direction substantially parallel to the contact line constituting the contact point M, preferably the main suction means 3. A method of suppressing the vibrations at both ends of the neck-in portion as described above is employed by performing suction with a suction force that does not exceed the suction force.
[0015]
The reason why the above-described vibration can be suppressed by providing the auxiliary suction means 4 is considered as follows. In other words, the reason why both ends of the neck-in portion vibrate is that, as described above, the outside air enters from the both ends of the contact point M at a considerable flow rate and flow rate with the suction from the main suction means 3. It is believed that there is. However, an auxiliary suction means 4 provided on both ends of the as contact points M illustrated, from the auxiliary suction means 4, when the substantially suction parallel way direction contact lines constituting the adhesion point M, for example, in FIG As schematically shown, a part of the outside air flowing in from both ends of the contact point M is guided and discharged to the outside by the auxiliary suction means 4, and the flow rate of the outside air flowing inward through the both ends of the contact point M is reduced. It is considered that vibrations at both ends of the neck-in portion caused by inflow of outside air can be suppressed.
[0016]
As a result of various studies by the present inventors, the vibration preventing effect of the auxiliary suction means 4 is such that the suction direction by the auxiliary suction means 4 is sucked in a direction substantially parallel to the contact line constituting the contact point M. It is confirmed that the vibration preventing effect as intended in the present invention cannot be obtained when the suction direction is perpendicular to the contact line, for example. The reason for this is not necessarily clarified, but if suction is simply performed in the vertical direction, that is, in the same direction as the suction direction of the main suction means 3, a part of the outside air that has once flowed in through the both sides of the contact point M is auxiliary suctioned. It will be considered that the vibration preventing effect is not effectively exhibited because the outside air flow rate that passes through both ends of the neck-in portion is substantially unchanged because suction is performed by the means 4. In order to effectively exhibit the above-described vibration preventing effect, it is most preferable to perform auxiliary suction in a direction parallel to the contact line. However, if it is about ± 10 ° , the suction direction is slightly oblique. However, it has been confirmed that a satisfactory anti-vibration effect can be demonstrated.
[0017]
The suction force by the auxiliary suction means 4 is desirably controlled so as not to exceed the suction force by the main suction means 3. However, if the suction force by the auxiliary suction means 4 becomes too strong, a large suction flow formed by the auxiliary suction means 4 is newly formed at the neck-in portion, and new vibrations are generated by this suction flow. It seems to do. In addition, if the suction force by the auxiliary suction means 4 becomes too strong, the suction force by the main suction means 3 becomes relatively small, and there is a risk of insufficient contact on the center side of the contact point M.
[0018]
On the other hand, if the suction force by the auxiliary suction means 4 is controlled so as not to exceed the suction force of the main suction means 3, vibration is caused by a new outside air flow by the auxiliary suction means 4, or at the central portion side of the contact point M. Without causing problems such as poor adhesion, vibrations at both ends of the neck-in part can be effectively suppressed, and accordingly, variations in the thickness and shape of both side edges of the film can be suppressed as much as possible. . In order to exhibit the vibration preventing effect by the auxiliary suction from the auxiliary suction unit 4 more effectively, it is most preferable to control the suction force within a range of about 60 to 100% with respect to the suction force of the main suction means 3. preferable.
[0019]
The shape of the suction port constituting the auxiliary suction means 4 is not limited at all, and any shape such as a circle, an ellipse, or a rectangle can be adopted. However, in order to exhibit the vibration preventing effect more effectively, A rectangular shape whose bottom surface is shaped according to the curvature of the cooling roll is most preferable so that a part of the incoming air can be efficiently sucked and exhausted from a position close to the surface.
[0020]
【Example】
EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a range that can meet the purpose described above and below. Of course, any of these is also included in the technical scope of the present invention.
[0021]
A T-die having a slit with an inner width of 260 mm is connected to the tip of a melt extruder having an inner diameter of 90 mm, and nylon 6 is melt-extruded from the slit, and a vacuum chamber (main suction means) is placed on a rotary cooling roll having a diameter of 900 mm. The film was rapidly cooled and solidified while adhering to it with a suction force from 100 mm, and a nylon film having a thickness of 100 μm was taken up at a speed of 35 mm / min. At this time, a suction nozzle (auxiliary suction means) having a suction port size of 10 × 30 mm is provided at both ends of the contact point in a direction perpendicular to the film winding direction, and suction is performed while suctioning from the vacuum chamber at 30 m / sec. With respect to the case of suction from the nozzle at a speed of 0 (no suction), 20 m / sec, or 30 m / sec, the variation rate of the thickness in the film width direction was measured by the following method.
[0022]
That is, 10m of nylon film 10m, which was rapidly cooled and solidified, was collected, and for each of the center positions divided into 7 equal parts in the width direction as shown in Fig. 5, the average thickness, the maximum thickness and the minimum thickness were measured. The thickness variation rate was determined by
Thickness variation rate (%) = [(maximum thickness−minimum thickness) / average thickness] × 100
[0023]
The results are as shown in Table 1. The thickness fluctuation rate when the suction from the suction nozzle is not performed (conventional example) is considerably large as 7.5%, while the assistance from the suction nozzle at a speed of 20 m / sec. If suction is performed, the thickness fluctuation rate can be reduced to 5.5%, and if the auxiliary suction is performed at the same rate of 30m / sec from the vacuum chamber, the thickness fluctuation rate is reduced to 5.1%. I understand that I can do it.
[0024]
[Table 1]

[0025]
【The invention's effect】
The present invention is configured as described above, and when the thermoplastic resin film is manufactured using the vacuum contact method, auxiliary suction means are provided separately from the conventional main suction means, and both end sides of the contact points are provided. By sucking and exhausting a part of the outside air entering through the auxiliary suction means, vibrations at both ends of the neck-in can be prevented as much as possible, and both side edges of the film that have been generated due to the vibration As a result, it was possible to produce a film with high homogeneity over the entire width direction by suppressing fluctuations in the wall thickness and shape as much as possible.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional explanatory view of a main part illustrating a film manufacturing situation employing the present invention.
FIG. 2 is a schematic explanatory view of FIG. 1 viewed from the right direction.
FIG. 3 is a schematic plan view showing an inflow state of outside air from a contact point.
FIG. 4 is a schematic perspective view for explaining the vibration suppressing effect at both ends of the contact point when suction from the auxiliary suction means is used in combination.
FIG. 5 is an explanatory view showing a position where the thickness variation rate of the film obtained in the example is measured.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cooling roll 2 Melt extrusion apparatus 2a Slit-shaped nozzle 3 Main suction means 4 Auxiliary suction means M Contact point

Claims

By melt-extruding a thermoplastic resin into a film form on a rotary cooling roll, and by a main suction means provided close to the upstream side in the rotation direction of the cooling roll in a contact line where the film starts to contact the cooling roll, In the process for producing a thermoplastic resin film that draws out air between the film and the cooling roll while sucking it out,
A method for producing a thermoplastic resin film, characterized in that auxiliary suction means are provided at both ends of the contact line, and the guide line is guided and discharged in an outer direction substantially parallel to the contact line.

The process according to claim 1, wherein the suction force of the auxiliary suction means is controlled so as not to exceed the suction force of the main suction means.