JPS61287721A - Cold high-orientation multi-layer film and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a laminated film capable of causing heat shrinkage in a low temperature, by a method wherein a laminate, having at least three layers consisting of the layer of ethylene series copolymer, the layer of copolymer of polyvinylidene chloride, low-density polyethylene or the like, is orientated in a high degree at a low temperature. CONSTITUTION:At least three layers of copolymer A of vinylester-ethylene such as the copolymer of ethylene-vinyl acetate, the copolymer B of aliphatic unsaturated carbonic acid or the ester thereof and ethylene or at least one kind of copolymer layer selected from ionomer-based copolymer C, derived from the copolymer B, the other layer consisting of a copolymer having the principal constituent of vinylidene chloride and other layer, consisting of a copolymer having the principal constituent of vinylidene chloride and different another layer, selected from saponified copolymer of low-density polyethylene, nylon, ethylene-vinyl acetate, are malted and laminated. This laminate is cooled suddenly and, thereafter, is orientated at a low temperature with the drawing ratio per unit area of 5-30X by employing a flow-regulating and -contacting guide.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates primarily to multilayer highly oriented films for use as packaging materials and their production.

Specifically, it has at least one layer containing a resin whose main component is an ethylene copolymer, at least one other layer containing a copolymer whose main component is vinylidene chloride, and a low-density polyethylene , polypropylene, nylon, or a saponified ethylene-vinyl acetate copolymer. The present invention relates to a highly oriented multilayer film and a method for producing such a multilayer film by highly stretching at a specific low temperature.

Conventional packaging methods using film include various packaging methods that take advantage of the characteristics of the film, such as sealing into a bag, twisting the film, shrinking by applying heat, and Saran wrap (Asahi Kasei Corporation). A large number of methods are used, such as the tight wrap method, stretch wrap method, and skin pack method represented by Co., Ltd. (product name), and each method requires its own packaging and characteristics. Currently, products are selected and packaged with appropriate material, composition, shape, characteristics, etc.

Among them, the shrink method utilizes the heat-shrinkability of a film that has been stretched and set in orientation, and after loosely pre-wrapping, for example sealing, the object to be packaged and enclosing the object, the film is exposed to hot air or infrared rays. This method involves heating and shrinking the contents using hot water or other heat medium to tightly adhere the contents. Its features are that the appearance of the package is beautiful and increases the product value, that the quality of the contents can be confirmed visually and tactile while keeping the contents sanitary, and that even irregularly shaped items or multiple items can be tightly fixed in one package. It can be packaged and has excellent protection against vibrations and shocks. Furthermore, compared to the stretch wrapping method currently widely used in supermarkets and the like, the wrapping speed can be increased.

It is also possible to package irregularly shaped items that cannot be wrapped with stretch wrapping, such as trays, etc. without containers. It also has the advantage of being able to be packaged more tightly, but has the disadvantage of having to be heated sufficiently until the film shrinks.

If the above-mentioned drawbacks can be solved, it is possible to create a packaging method that has more advantages than stretch packaging in terms of the area of use of the film, reduced internal thickness of the film, packaging speed, etc.

Problems to be Solved by the Invention Although the present invention does not particularly limit its use, shrink wrapping will be described below as a preferred example of its use.

Plasticized polyvinyl chloride (hereinafter referred to as PVC) is currently the most commonly used high-grade shrink wrapping film.
It is a stretched film. This is because it causes a high rate of heat shrinkage at relatively low temperatures and has the great advantage of being able to produce good shrink packaging over a wide heating temperature range.On the other hand, it has poor heat sealability and moisture resistance, and there are hygiene problems caused by plasticizers. The problem of deterioration over time, the generation of toxic gas such as chlorine gas when melted by heat rays, corrosive toxic gas when incinerating used film, and the problem of storing packages at low temperatures in cold regions. When handled in a cold environment, there are problems such as the film becoming hard, brittle, and easily torn due to its poor cold resistance.

Therefore, in recent years, polypropylene-based (hereinafter referred to as PP) films for shrink wrapping have attracted attention, but their drawback is that their shrinkability is inferior to that of PVC films. PP-based stretched films are excellent in terms of mechanical properties, moisture resistance, heat sealability, etc., and are excellent as shrink wrapping films.

Also, compared to PVC, it has advantages in terms of raw material cost and low specific gravity. However, PP is a crystalline polymer with a high softening temperature and a higher heating shrinkage temperature than conventional stretched films, and its shrinkage rate is small at low temperatures of around 100°C. Therefore, it is necessary to heat the product to a high temperature in the shrink packaging process, and the permissible range of heating temperature is narrow, and the shrinkage rate has a steep temperature dependence, so uneven heating in some areas during packaging can cause significant uneven shrinkage. It is easy to cause practical defects such as "wrinkles" and "pockmarks", and in order to prevent this, sufficient heating may cause overheating of the packaged material, devitrification of the film, holes due to melting, performance deterioration, and sealing parts. This has resulted in major drawbacks such as tearing of the air vent hole. Moreover, after packaging, the stress is released and the packaged item tends to loosen, and the film after packaging becomes hard and brittle.

In addition, conventional polyethylene films have not been able to impart sufficient stretching orientation to the molecules, and therefore, the obtained films have a low heat shrinkage rate, particularly a low heat shrinkage stress, and a high shrinkage temperature, making it difficult for the film to Its strength and optical properties are poor, and the cohesiveness of the packaged items after packaging is also low, so it is used in a thicker form for special purposes.

In addition, even in polyethylene films, films that are stretched at high temperatures using high-energy rays to sufficiently cross-link the molecules have a higher heat shrinkage rate and heat shrinkage stress, and are less transparent and glossy than regular polyethylene. It has very excellent properties such as optical properties and heat resistance, but it contracts in high temperature ranges and is prone to deterioration (particularly when its optical properties are large), and it also shrinks rapidly with temperature. It has disadvantages such as poor heat-shrinking properties, high degree of crosslinking that makes it difficult to heat seal, poor tear resistance and easy tearing, and difficulty in cutting with heating wire, resulting in poor packaging speed. As mentioned above, one of the important characteristics of shrink wrapping is that it can be wrapped sufficiently at low temperatures, which is particularly required when packaging fresh foods.

As mentioned above, the shrinkage temperature of the film (practically 20%
If the shrinkage is high, or if the shrinkage rate is large and rapid depending on the temperature, it is necessary to use a temperature that far exceeds the melting point of the polymer, especially in order to improve the finish of the packaged product. The film had to be packaged under very narrow conditions, and the film properties were severely degraded, causing problems.

On the other hand, in the case of polypropylene, the stretched film is produced by melt-extruding and quenching the tube-shaped raw material using an extruder, then reheating it to a high temperature of 150° to 160°C and introducing air inside. In the case of low-density polyethylene, the conventional method of biaxial stretching to set a high degree of stretching orientation is considered to be technically extremely difficult as it tends to tear during processing. There is.

For this purpose, for example, 180~
A common method is to extrude at a temperature of 220° C., then immediately expand it while cooling with air to form a film of a predetermined size.

This method has the feature of being able to easily produce films at a very low cost, but it tends to cause intermolecular flow (and it is not possible to set a satisfactory molecular orientation by stretching).
The optical properties are also inferior to those of large cloth. Therefore, the heat shrinkage rate and heat shrinkage stress are low and on the high temperature side, and it can only be used for special purposes by increasing the film thickness. For this purpose, after molding low-density polyethylene, it is irradiated with high-energy radiation under appropriate conditions to cause a partial crosslinking reaction, and then reheated to a high temperature exceeding its melting point (for example, 140°C) and stretched. Although there are methods of preventing intermolecular flow and setting sufficient molecular orientation, the degree of low-temperature shrinkability is low and the film tends to tear easily.

Also, recently, several attempts have been made to improve the shortcomings of these films. For example, special public service
No. 99 discloses a method of obtaining a stretched film by using a mixed composition of an ethylene-vinyl acetate copolymer and an ionomer resin and stretching the film at, for example, 100° C. to improve flow characteristics upon heating. With this method, the strength was also lower than that of the film of the present invention (tensile strength 4.2 kg/m
m2), the optical properties are inferior. Furthermore, the optical properties after shrinkage tend to deteriorate significantly. Also special public service 1977-40
No. 75 discloses a method of stretching using a specific ethylene-propylene copolymer, but the optical properties, heat shrinkage properties, strength, etc., and processability are still insufficient compared to PvC films.

Furthermore, various types of composite multilayer films are known as new packaging films.

Recently, due to the increasing sophistication of required characteristics, the trend is towards more and more complexities. For example, there are films that are almost unstretched or films that are stretched and melt-laminated with other resins.

For example, polypropylene (C
, PP) or stretched polypropylene (
0, PP) film with other resins melt-laminated to improve heat-sealability, or film coated with vinylidene chloride latex to provide barrier properties (referred to as K-coated film), depending on the application. A wide variety of films and combinations have been selected.

On the other hand, coextrusion films are generally known in which various resins are melted in separate extruders, merged and fused inside the die, extruded, and cooled to form a film or sheet. ing.

However, in order to obtain a highly stretched film for each of the layers that make up the multilayer, the optimal extrusion conditions, stretching conditions, etc. are different for each resin. Defects such as peeling and whitening due to interface roughness occur, and the desired characteristics of the film differ, making it extremely difficult to resolve these defects.

Means for Solving the Problems The inventors conducted research to further improve the shortcomings of these films and manufacturing methods, and found that the heat shrinkage properties, particularly the heat shrinkage rate at low temperatures, heat shrinkage stress, and heat shrinkage We have discovered an excellent film that simultaneously greatly improves the temperature dependence of properties, optical properties, film sealability, strength, etc., as well as a specific method for producing the same at low cost and with excellent processability.

That is, the present invention provides a multilayer highly stretched film comprising three or more types of polymer layers, in which one layer comprises the following copolymers (A) to
At least one copolymer selected from (C): (A) copolymer of vinyl ester monomer and ethylene; (B) aliphatic unsaturated carboxylic acid, aliphatic unsaturated carboxylic acid alkyl ester A copolymer of a selected monomer and ethylene; (C) an ionomer copolymer derived from the copolymer (B); the other layer is a copolymer mainly composed of vinylidene chloride. , and another layer contains the above copolymers (A) to (C
) at least one copolymer selected from the group consisting of at least one copolymer selected from the group consisting of a copolymer other than the above single layer, nylon, saponified ethylene-vinyl acetate copolymer, low-density polyethylene, and crystalline polypropylene. The present invention provides a cold highly stretched multilayer film containing a variety of polymers, having a tensile strength of 5 kg/++++n2 or more, and a shrinkage slope of 2.0 or less. It also relates to its manufacturing method.

The composite film of the present invention has the above-mentioned layers and is cold-stretched under specific conditions, thereby achieving a high degree of stretch orientation and excellent properties that are not found in other brands. It is characterized by the fact that it can be exerted by the synergistic effect of the two.

By combining the copolymers with different types of copolymers or with other types of resins, stretching conditions exceeding those of the single resins, that is, conditions that cannot be achieved alone, can be achieved, e.g. Under low-temperature conditions, a particularly high degree of stretch orientation is uniformly imparted to each layer in a very stable manner, and a film with particularly excellent strength, transparency, and other properties can be obtained.

The film of the present invention has good properties as a shrinkable film, although it is not particularly limited, as a variety of packaging films. In particular, it has excellent optical properties, strength, heat seal strength, and gas barrier properties, and is shrinkable at low temperatures. A film with excellent characteristics, shrinkage response (speed), etc. can be obtained.

The highly stretched film of the present invention is produced by extruding each of the above-mentioned polymers into a tube shape, for example, using a multilayer gouer containing at least three layers, and then rapidly cooling and solidifying the extruded product using, for example, a liquid refrigerant, and then heating it if necessary. It can be produced by cold stretching at a stretching temperature of 80° C. or lower and an area stretching ratio of 3 to 30 times.

One of the copolymers (A) that can be used in the present invention is
It is a copolymer of vinyl ester monomer and ethylene. The content of the monomer is preferably 3 to 13 mol%. A typical example of this copolymer is an ethylene-vinyl acetate copolymer, and particularly preferred is one having a vinyl acetate content of 3.5 to 12 mol % and a melt index of 0.2 to 6. More preferably, the vinyl acetate content is 4.0 to 11 mol% and the melt index is 0.2 to 4.

Other copolymers (B) include aliphatic unsaturated carboxylic acids and/or
Or it is a copolymer of a monomer such as the carboxylic acid alkyl ester and ethylene. The content of the monomer is similarly 3
It is 13 mol% to 13 mol%, preferably 3 to 12 mol%, and more preferably 4.0 to 11 mol%. These include copolymers of ethylene and at least one monomer selected from the group consisting of acrylic acid, esters of acrylic acid, esters of acrylic acid, esters of methacrylic acid, and the like.

The copolymer (C) refers to the above-mentioned ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-
At least a part of the copolymer selected from partially or more saponified polymers such as methacrylic ester copolymer and ethylene-acrylic ester copolymer is
", Zn", Mg", etc. are ionically bonded with metallic ions such as ", Zn", Mg", etc. Of these, the most preferable ones are ethylene-methacrylic acid ester copolymer, ethylene-acrylic ester copolymer. It is an ionomer in which at least a portion of a saponified substance is ionically bonded.

In the present invention, any mixture selected from the copolymers (A) to (C) can also be used.

A copolymer containing 3 mol% or less of a monomer other than ethylene does not have good cold stretchability, makes it difficult to achieve a synergistic effect, and tends to be punctured during stretching. or,
For the surface layer, sealability, optical properties, for the inner layer, strength,
Problems arise in interlayer adhesion and the like. On the contrary, 13
If the amount exceeds mol%, the elastic modulus of the film tends to decrease, particularly in the case of copolymers (A) and (B), and the heat resistance tends to decrease.

In addition, in the case of the surface layer, there is a tendency for blocking between the surfaces of the film. Furthermore, as the rubber properties become stronger and cold stretching is set, the orientation and dimensions tend to change at room temperature, which tends to result in poor strength, and the synergistic effect in multilayers also decreases. do.

In the case of the copolymer (C), although the rubber properties are not limited to those mentioned above, the stretchability is still reduced. Among copolymers (C), ionomer resins having partial ester bonds have good stretchability and have flexibility even when used as a surface layer, and may be preferable depending on the intended use.

Further, in the present invention, other suitable polymers may be mixed with the above-mentioned polymer composition. The copolymer then preferably has a
It is at least 60% by weight, more preferably at least 60% by weight, and even more preferably at least 70% by weight.

For example, the copolymer (C) may be mixed with a nylon resin or the like, such as a nylon 6-66 copolymer. Further, other suitable resins may be used as long as they do not inhibit cold stretchability. When used as a mixture, cold stretching is characterized by the fact that not only those with good compatibility but also those with slightly poor compatibility are stretched synergistically during stretching, resulting in a decrease in optical properties (in particular, a decrease in optical properties). Furthermore, it is surprising that not only is there often little decrease in optical properties (after shrinkage), but on the contrary, good properties are often exhibited synergistically. This relationship disappears more rapidly as the stretching temperature increases, and on the contrary, bad points begin to appear. That is, under the specific stretching conditions of the present invention, that is, 80°C
A film with excellent properties can be obtained by low-temperature stretching at a temperature below (for example, 35° C. below the softening point).

In the present invention, the above copolymer or a multilayer original fabric having a layer mainly composed of the copolymer is irradiated with high energy rays, and the copolymer is boiled as a xylene-insoluble gel of 0 to 70% by weight, with a melt index of 2 or less. After the treatment, cold stretching may be performed. In this case, the cold stretchability may be improved, and the web properties, particularly heat resistance, etc. may be improved, making it more desirable depending on the application.

The preferred range is 0.5 to 50% by weight of the insoluble gel and a melt index of 0.5 or less. More preferably,
The gel is 3 to 30% by weight, and the melt index is 0.07 or less. If the amount of insoluble gel is more than the above amount, the molded product will elongate, its strength will decrease, and it will deteriorate, especially when it is made into a film, the heat sealing properties will deteriorate, for example, it will not be sealed.
This results in problems such as the inability to cut with hot wire and the tendency to tear, so depending on the case, the above-mentioned degree is preferable.

In the multilayer film of the present invention, when forming a multilayer between different resins of the above-mentioned copolymers, the layer structure may be determined depending on the necessary requirements, but among them, each copolymer (A)
, when group C) is combined with group C) as a multilayer, it is often preferable to use copolymer (C) as the surface layer. The copolymer (C) generally forms a hard surface layer due to ionic bonds. This is also because it is more suitable in terms of sealability and optical properties. Next, as an example of a resin layer that is combined with a layer made of a resin other than the layer containing the copolymer, at least one layer containing a polymer mainly composed of polyvinylidene chloride (abbreviated as PDC) may be used. and/or nylon (abbreviated as Ny),
Crystalline polypropylene (abbreviated as PP), saponified ethylene-vinyl acetate copolymer (abbreviated as SEVA),
or other mixed polymers (e.g. crystalline polybutene-1)
At least one layer selected from the following. In particular, it has been found that when PDC is used as an intermediate layer, the barrier properties and pinhole resistance can be improved compared to those obtained by stretching at a high temperature according to the present invention. The ratio of the copolymer layer as a thickness structure of each layer is not particularly limited, and the lower limit is, for example, copolymer (C
) is used as the surface layer, when (A), (B), etc. are arranged as other layers, or when other resins with good cold stretchability are used, the copolymer layers generally have a content of 10% or more. Although this is not limited to the case of a multi-layer structure, if a layer other than the layer containing the copolymer is included, the ratio of the copolymer layer to the total layer is preferably at least 30%, more preferably at least 30%. The combination of layers having a thickness of at least 50% may be three or more layers, but preferably three or more layers. For example, (the copolymers (A), (B),
(C) is simply abbreviated as ASB, C) In the case of 5 layers, C
/B/PVDC/B/C,C/A/PDC/A/C,A
/B/PVDC/B/ASC/PB-1/PVDC/P
B-1/C, PP/PB/PDC/B/C5Ny/C
/PDC/A/C, etc.

These are effective for improving surface hardness, sealing properties, optical properties, etc., or for improving film stiffness, mechanical suitability for packaging, mechanical strength, etc., and are highly functional and expensive. For the seed resin, it is convenient if measures such as making this layer particularly thin and improving stretching processability are taken.

The film of the present invention can be cold-stretched, that is, in addition to biaxial stretching, it can be uniaxially stretched vertically or horizontally, but it is preferable to biaxially stretch in a bubble shape to obtain better stretch properties.

The film of the present invention has optical properties [haze value (AST
M-DI 003-52)] is generally below 3.0%, preferably 2.0%. This is a value that is characterized by its manufacturing method, and can be processed at low temperatures even below the melting point of the main composition, more preferably below the softening point, without impairing the quenched properties of the composition of the present invention. It is especially transparent because it can be stably stretched in a bubble shape. In addition, when used as a shrink film, the haze after shrinkage is
For example, shrinkage of 20 to 40% causes almost no deterioration, but many other films deteriorate significantly (for example,
PP is reduced from 2.8% to 6.5%, and crosslinked PE film is reduced to 2.5%.
5% to 4.8%). This value is preferably 4.0% or less, more preferably 3.0% or less after 20% shrinkage.

In addition, low-temperature shrinkability is one of the properties necessary when used as a shrink packaging film, and it is 20% or 40% of the value expressed by the heat shrinkage rate when the film is treated under one temperature condition. It is expressed as the temperature required for shrinkage (hereinafter expressed as the average shrinkage rate in length and width), and the lower this value is, the better the low-temperature shrinkage characteristics are. The shrinkage rate required for a shrink film usually varies depending on the packaging method, but is usually 20% or more, preferably 40% or more. Specifically, a square test piece cut from a film is marked with vertical and horizontal markings of specified dimensions, and the test piece is coated with powder such as talc to prevent it from sticking to itself or other objects during shrinkage. The heat shrinkage rate is the average value of the vertical and horizontal values expressed as the change rate of dimensions in each direction after heat shrinkage after being treated with hot air for 5 minutes, and this value is measured at each temperature. However, when graphed, the temperatures expressed by a heat shrinkage rate of 20% or 40% are referred to as 20% and 40% shrinkage temperatures, respectively.

When the film according to the present invention is used for shrink wrapping, this value is low; for example, the commercially available shrinkable polypropylene film mentioned below has a temperature of 120°C at 20% value and 134°C at 40% value.
In comparison, for example, as in Example I No. 1, it has characteristics as low as 49° C. at 20% and 72° C. at 40%. This degree is expressed as a 20% value and is 85°C or lower, preferably 75°C or lower, and more preferably 70°C or lower. This value is secondarily influenced by the stretching temperature, composition, layer combination, etc., but it is at a low level as one of the major features of the cold stretching of the present invention. If this value is high, thermal shrinkage will not occur until a long period of time at a considerably high temperature in practical use, requiring a large amount of heat from the heater and slowing down the packaging process. In addition, heat is transmitted to the packaged items, which is particularly undesirable for dangerous items or items that may be altered or deformed by heat, especially textiles and fresh foods. In addition, for films whose shrinkage curve tends to rise suddenly at high temperatures, the shrinkage rate changes greatly in response to very small changes around the shrinkage temperature during packaging, so if the film is loosely wrapped in advance and passed through a shrink tunnel, If the overall temperature of the hot air that hits the film is too low, the package will not shrink properly due to insufficient shrinkage, and if the temperature is too high, it will melt and cause holes or devitrification in the film, resulting in optical unevenness. It is common knowledge that the temperature of the film differs between areas that are in contact with the packaged item and those that are not, which can lead to unsightly pock-like shrinkage unevenness.
This will significantly reduce the product value.

Furthermore, if this temperature is high, not only the optical properties after shrinkage but also the mechanical properties such as strength will be significantly reduced.

Further, there may be problems such as the seal portion or the air vent hole being torn.

Moreover, if this value is too extremely low, the dimensions of the film wound into a roll may change at room temperature, which is not preferable. The commercially available PvC film for plasticized shrink packaging has this value of 58° C. at 20% shrinkage and 83° C. at 40% shrinkage, and has favorable shrinkage characteristics with low temperature shrinkage and gentleness with respect to temperature.

Shrinkage rates of 20% and 60% are values that represent the smoothness of the shrinkage curve, which is one of the other characteristics of sufficiently cold and highly oriented.
If the slope of the curve is expressed at the corresponding temperature between, that is, the shrinkage slope = (60-20)/Δt (%/1), the film of the present invention has a slope of 2.0 or less, preferably 1.5 or less, more preferably 1.5 or less. It is 1.3 or less. In addition, the shrinkage rate is small at 60%.
20-40 if near saturation or below
Let the shrinkage gradient be between %. In the case of biaxial stretching, this value is expressed as the average value of the vertical and horizontal directions, and the same applies to other properties hereinafter. However, in the case of -axis stretching, this is not the case, and the value is mainly in the direction of stretching.

Another characteristic is that the shrinkage rate at the Vicat softening point (hereinafter referred to as Vicat shrinkage rate) of the main association forming the film is at least 15% or more, preferably 20% or more, and more preferably 25% or more.

Vicat softening point is ASTM-Di 525 (load 1
kg). If this value is low, low-temperature shrinkability is insufficient for practical shrinkage, and the packaging temperature must be significantly increased. This will greatly soften the film and reduce the shrinkage stress to a large extent.
In addition, the product is exposed to temperatures above the melting point for a long period of time, making it impossible to package it uniformly and without wrinkles, and resulting in an unavoidable deterioration in string properties.

Another feature is that the film must already shrink sufficiently up to the crystal melting point of the main polymer constituting the film, and the film of the present invention fully satisfies this requirement. If this value is low, the product cannot be packaged unless it is sufficiently exposed to temperatures above that temperature during packaging. This value (referred to as mp shrinkage rate) is preferably 25% or more, more preferably 30%
or more, more preferably 35% or more, most preferably 40% or more
% or more.

A film other than plasticized PVC with such shrinkage characteristics and strength has never been commercially available.

The film of the present invention has achieved a level of properties higher than this and is a film that is unprecedented.

In addition, heat shrinkage stress during shrinkage is one of the important properties in heat shrinkage characteristics, along with heat shrinkage rate, when used as a shrink packaging film.For example, as described below, even if the heat shrinkage rate is high, If the stress at the time is extremely low, it will not fit the packaged items during and after packaging, and it will not have binding force.
It is completely useless as a shrink wrapping film.

Furthermore, if the binding force is insufficient even to a small extent, it is necessary to cover the objects with a thick film, which is uneconomical and inconvenient. As a feature of the film of the present invention, the peak value of this value is usually at least 50 g/n++n2.
Above, it is more preferably 100 g/+yun2 or more, more preferably 150 g/mm2 or more. For commercially available polyethylene shrink film, this value is 10g/mm2 or less, 5g.
/mm2, and its uses are limited. The film of the present invention has a run number of 210 g/m+n, such as Run No. 1.
There are also 2. Usually, the film of the present invention has this value of 100 to
It has a sufficiently high level of about 400 g/mI [12].

In addition, for low-temperature shrinkable films, this shrinkage stress has no meaning unless it is exerted from a temperature close to the level corresponding to the change in shrinkage rate, and the temperature dependence curve (expressed as the average value of vertical and horizontal values) is meaningless. It must be well balanced with the temperature curve.

In some cases, it may be preferable for the temperature to extend to a high temperature range. The temperature at the peak value of this stress is 90°C or less, preferably 80°C or less.
below ℃.

Furthermore, the present invention is characterized by its particularly high tensile strength and high elongation at break due to its manufacturing method, with a minimum of 5 kg/
mm2 breaking strength (value measured by the method of JIS-71702), preferably 7 kg/1TIII]
It has a value of 2 or more, and the elongation at that time is also 100
% or more, preferably 150% or more, more preferably 20% or more
0% or more, where y is the breaking strength (kg/
+n+n2), X is elongation at break (%).

Such high tensile strength and elongation mean that the film is tough and resistant to tearing, making it very advantageous as a protective film for packages and saving on film thickness.

The film of the present invention is, for example, Run No. 1, which will be described later.
5, breaking strength 14.5 kg/mm2, elongation 21
It is at a level of 0%. Normally, when the strength is increased by orientation, the elongation tends to decrease extremely. For example, a commercially available film that is fully crosslinked (67% boiling xylene insoluble gel) and stretched at high temperature has a strength of 8 kg/mm2 and an elongation of 45%, making it easy to tear. . Also, falling cone impact strength (referred to as dart strength)
It is measured according to ASTM-DI 709-67, and because it is difficult to measure without tearing with normal methods, it is expressed as a value using a sharp special head with a grooved edge on the missile head to make it easier to tear the film. is characterized in that this value is particularly strong. For example, contraction PV
Although the CSPP film is 16 kg-cm and 8 kg-cm, Run No. 15 is actually 32 kg-C.
m or more (all calculated in terms of 17μ), which is comparable to low-density P'E commercially available heavy packaging with a thickness of 100 to 150μ. This value is generally 15 kg-cm or more, preferably 20 kg-cm (hereinafter converted to 17 μm). High tensile strength and elongation mean that the film is tough and difficult to tear, making it very advantageous as a protective film for packages, a film for skin packs, etc., and it can save on film thickness. . The film thickness is not limited, but is usually 5 to 200μ, preferably 8 to 1
It is 00μ.

The application is not limited to shrinkage films, but can generally be used as industrial films using Kufunesu.

Next, a preferred example of the method for producing a highly stretched film of the present invention will be described in detail.

The method of the present invention involves heating, mixing, and melting the above-mentioned copolymers, extruding them through a multilayer annular gouer, and rapidly cooling and solidifying them with a liquid refrigerant to obtain a tube-shaped original fabric with sufficiently small thickness deviation. After treatment with energy rays, it is left as it is at room temperature or heated slightly, and then cold stretched at a stretching temperature of 80°C or less and an area stretching ratio of 5 to 30 times (the stretching temperature here refers to the temperature at the starting point of stretching). ). Here, the stretching is carried out using a rectifying contact guide designed to substantially isolate the stretching start part and the heating part, while at least discontinuously contacting and removing the fluid accompanying the film surface and its film in the circumferential direction. .

Preferred embodiments will be described below, but the present invention is not limited thereto.

Extrusion is carried out by using a multilayer annular goo, which does not give sufficient unevenness in thickness, heat, or time history, at an extrusion temperature of 150 to 280°C, and uniformly quenching and solidifying the surrounding area with a liquid refrigerant. (also) into a tube-shaped raw material. This raw fabric may be pretreated with high-energy radiation, for example, with electron beams, gamma rays, ultraviolet rays, etc., for example, at a dose of 1 to 10 megarads. Excessive treatment may actually have negative effects on various properties.

Next, the stretching is carried out at room temperature as it is, or by heating if necessary, at a temperature at which the main crystals of the main polymer, and preferably the main crystals of the polymers forming each layer, melt (the peak value determined by the DSC method). (measured at a scanning speed of 20°C/min).The reason for this is that once a crystal is melted, when the temperature rises and falls at a fast rate, the hysteresis effect causes the crystal to reach a temperature considerably lower than its melting point. This is because the crystallization occurs at the crystallization temperature, making it difficult to provide sufficient cold orientation. For example, this tendency is particularly strong in ionomer resins, and the Na-crosslinked type methacrylic acid content: 5.4 mol%, melt index: 1.3, density 0.942 g/am3 made of ethylene-methacrylic acid is At a scanning speed of 20°C/min (the actual film formation speed is much faster), the peak at the melting point of 100°C may have a peak at the crystallization temperature of 50°C, but if the crystallinity is low, this Not as long.

In the present invention, the stretching is generally 80°C or less, preferably 20 to 7
It is preferred to stretch at a very low temperature of 0°C, more preferably 20-60°C, and at the same time, more preferably below the Vicat softening point of the polymer. That is, the temperature is preferably 10° C. or lower, more preferably 15° C. or lower than the Vicat softening point. It is preferable to stretch the film properties at as low a temperature as possible for processing stability.Stretching at temperatures above the above-mentioned upper limit will rapidly deteriorate various properties and also worsen stretching stability, resulting in non-uniformity such as uneven thickness and valve wobbling. The phenomenon begins to occur. In terms of properties, the low-temperature shrinkability, shrinkage gradient, etc. referred to in the present invention deteriorate, and the optical properties, strength, elongation, and other properties such as pinhole resistance in the case of barrier films also deteriorate significantly. During heating and stretching, it is preferable to uniformly blow air whose temperature is controlled by an air ring or the like, and to control the air flow in the surface layer as uniformly as possible. The heating temperature of the original fabric is 20° below the temperature at the start of stretching.
Preferably, the temperature does not exceed °C. Further, it is often preferable to conduct the stretching with a temperature difference of at least 5° C., preferably 10° C., between the stretching start point and the stretching end point.

One way to control the air flow in the surface layer is to use a rectifying contact guide, which is designed to substantially isolate the heating area and the stretching start area, to control the fluid (gas) entrained on the surface of the film and its surrounding film. There is a method of discontinuous contact removal in the direction to remove non-uniformity due to interaction between the heating section, the stretching start section, and the cooling section. This method can also be used in the stretching start section, stretching section, and stretching end region. It can be done. The internal pressure inside the valve is high;
For example, 10 (] - 5000 mm water column pressure (H2C) (
It is preferable to stretch sufficiently under a high pressure of 200μ and 100mmφ, more preferably 200 to 2
000mm (H2C).

Further, the stretching ratio is 5 to 30 times in area stretching ratio, preferably 5 to 30 times in area stretching ratio, and 2 times in transverse direction.
~7 times. More preferably, the former is 7 to 20 times, and the latter is 2 to 5 times.

At this time, as mentioned above, it is important to make a sufficiently uniform raw fabric. For example, the uneven thickness of the raw fabric is ±10% of the thickness of the raw fabric.
If the thickness is above or below this level, punctures may occur during stretching, resulting in poor stretching. Uneven thickness of raw fabric is preferably ±5%
It is more preferably ±2% or less. The degree of stretching is determined by the speed ratio of the feed nip roll and the take-off linip roll, and the stretching ratio in the vertical direction is determined.Then, air is sealed in the bubble and the bubble is stretched until it reaches the end point of stretching (just before whitening), and the expansion in the lateral direction stops. The most stable method is to stretch at a certain level. In addition, the raw fabric bubble has a diameter of about 50 mm or more, preferably 100 mm or more due to the relationship between internal pressure and diameter.
It is convenient to use a large size with a diameter of mm or more as long as the device allows.

In addition, in view of the physical properties of the obtained film, it is preferable to keep the film sufficiently cold as long as the stability of the bubbles allows, but in reality,
The stretching temperature may be determined by making some adjustments depending on the composition at the time, in balance with stability (avoiding punctures).

The film obtained by the method of the present invention has excellent physical properties as described above, and at the same time, the thickness deviation of the film after stretching is very small, often about ±5% or less. This is thought to be because the high bubble internal pressure imparts a strong tensile force to the film, so that the thermal history of heating and cooling as in the case of ordinary textiles is particularly small, resulting in uniformity and good stability. Even if the optical properties (both haze and gloss) appear somewhat poor at the raw stage, they become much better after cold stretching by the method of the present invention. Furthermore, by using multiple layers as described above, processing stability is greatly improved compared to when using a single layer, and more uniform and sophisticated products can be produced.

In comparison to the above, in the stretching method in which heating is performed above the normal melting point,
This does not happen, and in order to improve the optical properties, it is necessary to increase the stretching temperature.
In many cases, orientation becomes increasingly difficult and strength tends to decrease.

Moreover, the same thing can be said at temperatures of ±5 to 10°C around the melting point, and not only will the optical properties not be even more favorable, but in addition, in the case of mixed compositions, the temperature conditions will make the original fabric particularly brittle, resulting in punctures and high properties. Difficult to grant.

It is not in the name of the present invention that the stretching referred to in the present invention can be successfully achieved at a cryogenic temperature, for example, 31° C., as in the later-described examples of the present invention, but by using, for example, a multilayer tube containing the specific copolymer, This is achieved for the first time through the synergistic effect of using a uniformly quenched original fabric and satisfying conditions such as a specific stretching method.

For example, in the case of a single PP layer, continuous stretching is achieved only under a very narrow range of about 140 to 160°C, which is difficult and delicate, and below which it cannot be stretched due to punctures. Moreover, if the temperature is higher than that, a whitened, weak and inferior film cannot be obtained, and if the temperature is lower than that, around 80°C, let alone, as in the case of the above example, 32°C, it is difficult to achieve stretching at all, which is surprising. That's a thing.

In addition, the properties obtained are superior to those of a single layer in terms of strength, optical properties, low-temperature shrinkability, sealing properties, tear strength, impact strength, etc., and the level of stretching is higher than that of normal stretching. .

In addition, after the film of the present invention has been stretched, it can be freely heat-treated, for example, on-line, after winding, etc., and when stored near room temperature, for example, to prevent dimensional changes and collapse of the roll when it is wound into a roll. It can be stabilized and components that shrink at room temperature can be cut. Furthermore, depending on the degree of treatment, components that shrink at low temperatures can be freely controlled without degrading other physical properties. Furthermore,
It is also possible to freely move the orientation vertically or horizontally using a biaxially stretched film.

Examples Experimental Example 1 Vinyl acetate group content: 5.5 mol%, melt index: 0.6, crystal melting point (hereinafter abbreviated as mp) 788°C,
Vicat ethylene-vinyl acetate copolymer (a,) with a softening point of 72°C and ethylene-methacrylic acid copolymer Na
Type Iomer resin dimethacrylic acid content 6.6 mol%, melt index 1.0, neutralization degree 25%, mp8
3°C and Vicat 64°C (C1) using two extruders, the former having a screw with a diameter of 35a + mL/D = 30, and the latter having a screw with a diameter of 40 mm and L/D = 30. So, the maximum temperature of part of the cylinder is 24
They were each plasticized and melted at 0°C, extruded through a 100 mm diameter two-type, three-layer annular goo with a 15 mm slit, and quenched with a water-cooling ring that uniformly discharged water 10 cm from the end of the goo to form the first layer (100 mm in diameter). outer layer), second layer (
Raw fabrics having the respective thicknesses shown in Table 1 were obtained with each composition of the intermediate layer) and the third layer (inner layer). In all cases, the thickness deviation (circumferential direction) was ±2% or less. These raw fabrics are passed between two pairs of feed nip rolls and take-up nip rolls, heated to 37°C by hot air between them, air is admitted inside, and continuously expanded using the aforementioned rectifying contact guide. Stretch it 345 times vertically and 3.5 times horizontally, cool the stretched area with an air ring blowing cold air at 15℃, fold it with a deflake, pull it with nip rolls, and slit the edges vertically. The film was divided into two films and each film was wound up with a constant tension to obtain a film of each thickness.

Table 2 describes the characteristic values of the obtained film in comparison with three commercially available films serving as comparative examples.

Table 1 *However, both mp and Vicat shrinkage rates are expressed using the resin with a higher layer ratio as the main layer.

Comparative sample 0 is a commercially available PVC shrink film,
○ indicates the same PP shrink film, 0 indicates the same crosslinked polyethylene shrink film.

All of the obtained films showed excellent properties and had properties superior to that of the O1O film of the comparative example. In addition, the resulting various films were used as shrinkage films for cucumbers, and the packages were wrapped using a commercially available L-shaped sealer and passed through a commercially available tunnel that emitted hot air at 90°C for 1 second.
It was a tight, wrinkle-free fit, had a good packaging finish, and had no deterioration in optical properties after shrinkage, allowing for beautiful shrink wrapping. Further, as a result of testing by varying the residence time in the hot air temperature tunnel during shrink wrapping, results were obtained that the wrapping could be performed well over a wide temperature and speed range starting from the low temperature side.

Compared to the above, commercially available polypropylene shrink film has 12
Even at 0℃, there is almost no shrinkage and wrinkles remain on the sample, and under the same conditions, the hot air temperature must be increased and the temperature is passed for 5 seconds at 18.0℃ to achieve sufficient shrinkage. Even if the residence time was extended, the film would have holes and breakage, and the film would become devitrified, so the appropriate temperature range was very narrow, but the optical properties of the film in this sample did not shrink. There is almost no change after that, for example, R
un Nα2 was 0.7% after 40% contraction. Also, commercially available PVC shrink film still does not shrink enough under the same conditions.
Wrinkles remained, and it was necessary to set the temperature condition to 160° C. for 4 seconds. It was also found that the shrinkage curve showed faster response than PVC even at the same level. Film strength, elongation,
In the case of biaxial stretching, the heat shrinkage properties show well-balanced properties in both the longitudinal and transverse directions, so they will be expressed as the average value in the longitudinal and transverse directions.

In addition, as a comparative example, when trying to stretch the original fabric of Run Nα2 at a stretching temperature of 92°C, the neck part was bent during stretching, and it was very unstable and easily punctured, making it impossible to stretch it successfully. (Comparative example Run No. 1
). When I measured the haze of a small piece of this film, it was 6.
．． It was a film with poor transparency having a high value of 8%. The shrinkage stress value was also as low as 40 g/mm2.

Bubbles were continuously formed only when the stretching temperature was set to 135°C. This film has a haze value of 5.9%, no low temperature shrinkage, a shrinkage slope of 4.8, a 20% shrinkage rate of 89°C, a Vicat shrinkage rate of 14%, and a shrinkage stress of 12 g/
Tensile strength in mm2 is 3.5 kg / mm2 elongation 4
It was 90% and could not be called a highly oriented film. An attempt was made to stretch the original fabric of Run No. 3 at a stretching temperature of 85° C., but the bubbles during stretching were unstable and easily punctured. Also, the optical properties are poor, with a haze value of 8.5%.
The film had a low tensile strength of 4.3 kg/mm2 and low low-temperature shrinkability.

Experimental Example 2 In the same manner as in Experimental Example 1, original fabrics were obtained using the combinations of layers having the compositions shown in Table 3 using three extruders, three types of three-layer die, and three types of five-layer die. After the raw fabric of Run Nα11.12 was irradiated with an electron beam as an energy beam, the other raw fabrics were subjected to cold stretching at a stretching temperature as described below to obtain a film.

The properties of these films are shown in Table 4.

Here, al, cl are the above-mentioned C2 is an ethylene-vinyl acetate copolymer (6.7 mol% based on vinyl acetate group content, melt index: 1.2, mp:
83°C, Vicat: 63°C); bl is ethylene-dityl acrylate copolymer, acrylic acid base 1: 5.8 mol%, melt index: 2.
0, mp: 82°C, Vicat: 67°C); b2 is a partially saponified product of ethylene-methyl methacrylate copolymer (methyl methacrylate group content = 7, 0 mol%, melt index: 5, mp :84℃
, vicat: 64°C); C2 is partially saponified ester-methyl methacrylate copolymer (40°C);
%) Iomer resin (Na type) consisting of a polymer (methacrylic acid and ester group content near, 0 mol%, melt index: 1.
0, mp: 90°C, Vicat 56°C); PE is low density polyethylene (density: 0.917g
/cm3, melt index 0.4, mp+108℃
, Vicat: 90°C); PB is crystalline polybutene-1 (density: 0.905 g/Cm3, butene-1
~97 mol%, mp: ti7, Vicat: 10
8℃); PP is crystalline polypropylene (density 0.8℃); PP is crystalline polypropylene (density 0.8
8 g/cm3, propylene: 97 mol% modified with ethylene, melt flow rate = 6.0, mp: 150°C, Vicat
: 145°C); EPE is an ethylene-α-olefin copolymer elastomer (
α-olefin is a random copolymerization of 15 mol% propylene and 2% by weight ethylidenenorbornene, melt index 0.45 density 0.88 g/Cm3): Ny+ is nylon 6.66 copolymer; SE V A +i ethylene 55 mol % vinyl acetate copolymer (EVA) with a degree of saponification of 98%*1)? The 31st layer is G by Mrad's electron beam irradiation treatment.
el is 48% by weight, *2) 02,') by 8 Mrad electron beam irradiation treatment
The two layers each contain 45% by weight and 25% by weight of Gel.The temperature during stretching was 4 for Run No. 6 to 12, respectively.
At 6.33.51.31.39.35.42°C, the horizontal stretching ratio was approximately 3 to 4 times, and the vertical stretching ratio was 2.8 to 4 times, and stable stretching was possible in both cases. All of the obtained films had excellent properties, particularly excellent optical properties and strength properties.

Regarding Run No. 6.7, we conducted a practical packaging test using 3 carrots in the same way as in Example 1, and as a result, 0 with hot air at 80°C.
．． After just 8 seconds of processing, a packaged product with excellent optical properties and a good finish was produced. In addition, the commercially available ωpvc mentioned above
, ■Each sample of PP10 crosslinked PE and RunNIIL6
vertically at the appropriate shrinkage temperature for each film.
Conclusion of examining the haze value after shrinking by 20.40.60% in the average horizontal dimension ■PVC1, 9, 2, 0, 2, 3%, ■P
2.8.6.5.11.0% with P, 0 crosslinked P E 2.
5.4.8.6.5%, all of which are greatly deteriorated in many cases, but Run No. 6 is 0.7,), 8.0.9
It showed an excellent value of %.

In addition, tests were conducted at various stretching temperatures using the original fabric of Run No. 6. At 85 to 90°C, bubbles were unstable and prone to puncture, the optical properties, low-temperature shrinkability, and strength were poor, and the haze was 7.
6%, 20% shrinkage rate 84℃, tensile strength 3.9 kg/
It was mm2. Stretchability of about 40 to 60° C. was preferable in terms of stability, film optical properties, and other properties.

Example 1 A raw film was obtained using the combinations shown in Table 5 in the same manner as in Experimental Example 2, and the film was stably formed at a stretching temperature of 32.35.40.55°C with Run No. 13.14.18.19. I got it. The properties of this product are shown in Table 6.

Table 5 here a l, C2, NVI, PPt PBt, b2
ttM$PDCI is a vinylidene chloride copolymer: a 10% by weight copolymer of vinyl chloride; PDC2 is a vinylidene chloride copolymer copolymerized with nialic acid; b3 is an ethylene-methacrylic acid copolymer (Methacrylic acid group content near, 0 mol% melt index 5, mp: 83°C, Vicat: 62°C)
The outer layer is 16μ EVA, and the inner layer is 36μ irradiated EVA.
film.

The samples of each Run No. had better optical properties, low-temperature shrinkability, shrinkage stress properties, tensile strength, and impact strength than the comparative samples, and also had better barrier properties. After vacuum packaging 3 kg of processed meat as a practical test, 8
By placing the package in a hot water shower at 0° C. for 3 seconds, a tightly shrinkable package with good shelf life was obtained.

As RunNα21, the 1st to 5th layers are C2+Ny, the mixing ratio is 80/20, the weight ratio is the 1.5th layer, the middle layer is PDCI, the 2.4th layer is C2, and the thicknesses of the 1st to 5th layers are respectively increased. 100150/100150/150 (in order of layers)
μ), the same method was used to stretch at 47°C, resulting in stable stretching. Haze: 1.1%, 20% shrinkage temperature: 58°C, shrinkage slope: L 1 , Vicat shrinkage rate = 38%, maximum shrinkage rate 79 % shrinkage 250g/m+n2, tensile strength: 15. Okg/mm2, elongation 210%, falling strength 90 kg-cm or more, 02 barrier property: 25cc
A 50μ film of /m2·24hr-atm was obtained.

As a result of practical packaging of this film, similarly excellent packaging results were obtained.

As Run No. 22, the original fabric No. 13 and the original fabric No. 14 were irradiated with an energy beam of 5 Mrad using an electron beam, and Al was 6% by weight of Gel and C.
No. 2 was subjected to a low degree of crosslinking treatment to give a melt index of 0.05 or less to GelIO weight %. At this time, with this level of treatment, almost no decomposition of the second and third layers was observed.

This original fabric was stretched under the same conditions, and a stable film was obtained. The film exhibited properties similar to those before treatment. However, the tensile strength and impact strength were improved by about 20%.

As a comparative example, we tried stretching at 100°C using a raw fabric with Run No. 13.14, but the stretching did not continue for a long time due to punctures, and unstretched streaks appeared in the vertical direction, so it was not successful. There wasn't. Also, the film was whitish and had poor optical properties, haze of 13%, and tensile strength of 4.5 kg/
It was a film with a low thickness of mm2.

Further, although stretching was attempted at 85° C., bubble bending occurred and the film was immediately punctured, making it impossible to continue stretching. At temperatures from 80 to 66°C, stretching was possible although there were occasional punctures, and below that temperature, from 30 to 50°C, the stretching was most stable as described above, and the physical properties were good. In addition, commercially available film of ratio ①, film at 100°C,
When the 02 barrier property was measured after repeatedly bending the film in Run No. 3.14 by hand-wrapping it, it was found that the film in Run No. 13.14 showed almost no deterioration; The film is 2
．． It was three times worse. This shows that the highly cold stretched film of this example has particularly excellent pinhole resistance in the barrier layer. This seems to be because the barrier layer is also stretched at a sufficiently low temperature.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between film shrinkage rate and heat treatment temperature, and FIG. 2 shows the relationship between film shrinkage stress and heat treatment temperature. (In the figure, 1 is a film of Run Nα3; 2 is a film of Run Nα14; 3 is a commercially available plasticized PVC
Shrink film; 4 is a commercially available PP shrink film; 5 is a commercially available crosslinked polyethylene shrink film:
6 is the commercially available barrier shrink film mentioned above)

Claims (8)

[Claims] (1) In a multilayer highly stretched film consisting of three or more types of polymer layers, one layer is at least one type of copolymer selected from the following copolymers (A) to (C): (A) Vinyl ester monomer (B) A copolymer of ethylene and a monomer selected from aliphatic unsaturated carboxylic acids and aliphatic unsaturated carboxylic acid alkyl esters; (C) The above copolymer (B) ) is an ionomeric copolymer derived from , another layer contains a copolymer mainly composed of vinylidene chloride, and another layer contains the above copolymers (A) to (C
) at least one copolymer selected from a copolymer other than the above single layer, nylon, saponified ethylene-vinyl acetate copolymer, low-density polyethylene, and crystalline polypropylene. 1. A cold highly stretched multilayer film comprising a certain polymer, having a tensile strength of 5 kg/mm^2 or more, and a shrinkage gradient of 2.0 or less. (2) At least one copolymer selected from the following copolymer groups (A) to (C): (A) Copolymer of vinyl ester monomer and ethylene; (B) Aliphatic unsaturated A copolymer of ethylene and a monomer selected from carboxylic acids, aliphatic unsaturated carboxylic acids, and alkyl esters; (C) An ionomeric copolymer derived from the copolymer (B). , another layer contains a copolymer mainly composed of vinylidene chloride, and another layer contains the above copolymers (A) to (C
) at least one copolymer selected from the group consisting of at least one copolymer selected from the group consisting of a copolymer other than the above single layer, nylon, saponified ethylene-vinyl acetate copolymer, low-density polyethylene, and crystalline polypropylene. A multilayer molten original fabric containing a seed polymer is extruded, and this is rapidly cooled and solidified using a liquid refrigerant to form a multilayered original fabric, and the obtained original fabric is stretched as it is or at a stretching temperature of 80°C or less by heating with the stretching start part. Using a rectifying contact guide for the purpose of substantially isolating the film surface, the film is cold-stretched at an area stretching ratio of 3 to 30 times while contacting and removing the fluid entrained on the film surface and its film at least discontinuously in the circumferential direction. A method for producing a multilayer highly stretched film, which comprises stretching. (3) The method according to claim (2), in which the multilayer original fabric is heated to a temperature below the crystalline melting point of the main polymer. (4) The method according to claim (2), wherein the multilayer original fabric is stretched at a stretching temperature of 20 to 70°C. (5) The method according to claim (2), (3) or (4), wherein the multilayer original fabric is stretched at a temperature below the Vicat softening point of the main polymer. (6) The method according to claim (2), wherein the multilayer original fabric is a tubular original fabric and is stretched at a transverse stretching ratio of 2 to 7 times. (7) The method according to claim (2) or (6), wherein the stretching is carried out at an area stretch ratio of 7 to 20 times and a transverse direction stretch ratio of 2 to 5 times. (8) Stretch at least 5 times more at the end of stretching than at the beginning of stretching.
Claim No. (2) which is performed by creating a temperature difference that is as low as ℃
The method described in section.