JP3189174B2 - Composite stretched film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention has a gas barrier property,
The present invention also relates to a novel composite stretched film having excellent mechanical properties and sealing properties. Further, the composite stretched film of the present invention is mainly used for various packaging materials (mainly, household wrap film, non-shrink wrapping film utilizing barrier properties, shrink wrapping film, laminate film, and other uses are not limited). It can be suitably used for.

[0002]

2. Description of the Related Art Conventionally, as packaging films, polyvinyl chloride, polypropylene, polyethylene,
There are films using polyamide, polyester, etc.
As a film having particularly excellent gas barrier properties, a composite film using a gas barrier polymer such as a vinylidene chloride-based resin or an ethylene-vinyl alcohol-based copolymer is known.

[0003] However, these composite films are mainly used in the food field in accordance with the required level of gas barrier properties in order to suppress the deterioration and decay of the packaged articles and to secure the quality over a long period of time. It is widely used as various packaging materials such as chemicals, and further, for packaging electronic parts and the like.

[0004] However, films using these conventional gas barrier polymers have the following problems, respectively. That is, in the case of vinylidene chloride resin, for the extrusion stability at the time of film production,
In order to give good stretchability, it is usual to add a large amount of a plasticizer or a stabilizer, and these are not preferable in terms of hygiene and have problems of odor and discoloration.

[0005] In addition, in the case of a multilayer film, if necessary, these additives migrate to an adjacent layer, and the barrier properties become unstable with time. Furthermore, similarly, in the case of a multilayer, a cross-linking treatment may be performed by irradiation with an energy beam such as an electron beam for the purpose of improving the heat sealing property and the stretchability. On the other hand, it is liable to deteriorate and discolor, and such a treatment is disclosed in International Publication WO 87/07880 (Patent Application Publication No. 64).
Extremely strict and complicated management as disclosed in the specification is required. Also, disposal,
There are also environmental conservation and hygiene issues associated with incineration.

Next, the ethylene-vinyl alcohol copolymer does not have environmental health problems as the vinylidene chloride resin has and the gas barrier property at the time of drying is generally superior to that of the vinylidene chloride resin. Use for various packaging films is being studied.

The ethylene-vinyl alcohol-based copolymer referred to herein is mainly composed of ethylene and vinyl acetate as disclosed in JP-B-47-38558 and US Pat. No. 3,510,464. Is a copolymer obtained by hydrolyzing or saponifying the above-mentioned copolymer, and is essentially different from a copolymer containing hydroxymethylene units obtained by reducing the polyketone of the present invention.

This ethylene-vinyl alcohol copolymer generally has difficulty in processability, and exhibits a necking-like (concurrently involving extremely thick and thin portions) stretching at the time of stretching, resulting in stability of film formation. However, it tends to break easily, and it is difficult to make the film thin. In addition, there is a problem in thermal stability, and gel is easily generated when melt extrusion is performed continuously, which adversely affects subsequent processing (for example, occurrence of breakage during stretching and film formation of a film) and lowers commercial properties. There are problems such as invitation.

[0009]

Accordingly, the present inventors have:
As a result of various examinations of the above-mentioned problems, it was found that a composite stretched film in which a specific polyketone-reduced hydroxymethylene unit-containing copolymer (B) layer was laminated on a polyolefin-based resin (A) layer, thereby improving melt processability and stretchability. It has been found that a novel gas barrier film which is excellent in film properties, can be easily formed into a thin film, and is excellent in mechanical properties, optical properties and the like can be obtained, and has completed the present invention.

That is, the present invention relates to a stretched composite film comprising: (A) a layer mainly composed of a polyolefin resin; and (B) a layer containing a copolymer having hydroxymethylene units as a component. The hydroxymethylene unit is obtained by reducing at least a part of the carbonyl group of the polyketone, and the polyketone is formed by reacting carbon monoxide with at least one α-olefin having 2 or more carbon atoms. Copolymer or copolymer of carbon monoxide and at least one α-olefin with at least one monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acids and aliphatic unsaturated carboxylic esters Is provided.

In a preferred embodiment of the present invention, the polyolefin resin constituting the layer (A) includes a polypropylene polymer, a poly-4-methylpentene polymer, a polybutene polymer, a polyethylene polymer, Ethylene-α-olefin copolymer, soft polymer composed of α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester Copolymer or the like, or a copolymer composed of two or more kinds freely selected from each monomer of the above copolymer, or at least one selected from modified polymers of these polymers Is desirable.

In the present invention, an intermediate layer (C) composed of a polymer different from the (A) layer and the (B) layer may be provided. It is desirable that the ratio of the copolymer contained in the layer (B) constituting the composite stretched film of the present invention is 10 to 100% by weight.

Further, the content of hydroxymethylene units obtained by reducing the polyketone constituting the copolymer contained in the layer (B) is 10 to 50 mol%, and the content of the hydroxymethylene unit contained in the layer (B) is It is desirable that the hydrogenation conversion of the copolymer be at least 50%. Further, it is desirable that the composite stretched film has at least one layer of the film crosslinked.

Hereinafter, the present invention will be described in detail. The polymer layer (A) of the present invention is used as a reinforcing layer in terms of mechanical strength such as tear strength, and when disposed on a surface layer, further as a heat seal layer and as a protective layer of the (B) layer. In addition, an antifogging agent, an antistatic agent, a lubricant, etc., as additives, are added to the resin constituting the layer (B) to serve as a surface layer for bleeding, and in some cases an adhesive layer as an intermediate layer Can also be used. Preferably, it is arranged such that one of the surface layers is the (A) layer.

The polyolefin resin as a main component of the polymer layer (A) includes a polypropylene polymer, a poly4-methylpentene polymer, a polybutene polymer, a polyethylene polymer, ethylene-α- Olefin copolymers, soft polymers composed of α-olefin copolymers, ethylene-vinyl acetate copolymers, ethylene-aliphatic unsaturated carboxylic acid copolymers, ethylene-aliphatic unsaturated carboxylic acid ester copolymers, Or a copolymer consisting of two or more freely selected from the monomers of the above copolymers, or a modified polymer of these polymers, and at least one selected from these is used. However, other polymers may be mixed as long as the properties are not impaired. Its amount is less than 50% by weight, preferably not more than 30% by weight.

Preferred examples of the polypropylene-based polymer include known homopolypropylene and copolymers of polypropylene with other α-olefins (C ₂ , C _{4 to} C ₈ ). Examples of the poly-4-methylpentene-based polymer include poly-4-methylpentene-1 and 4-methylpentene-1 and a small amount of other monomers such as α-olefins (C _{2 to} C ₁₂ ). Having a transparency of, for example, a density of about 0.835 g / cm ³ , a visible light transmittance of 85% or more, and a Tg of about 50 ° C. or less.

The polybutene-based polymer is a crystalline polymer having a butene-1 content of 85 mol% or more and having other properties (carbon number C ₂ ,
It has a high molecular weight including a copolymer with a monomer of C ₃ , C _{5 to} C ₈ olefin, and has a melt index (1) unlike liquid and waxy low molecular weight ones.
(At 90 ° C. and 2.16 kg), preferably from 0.1 to 10.

Typical examples of the ethylene-based polymer include ordinary low-density polyethylene and high-density polyethylene. As the ethylene-α-olefin copolymer, linear low-density polyethylene, ultra-low density (VL, U
L) polyethylene, etc., which are ethylene and propylene, 1-butene, 1-pentene,
It is a copolymer with at least one monomer selected from α-olefins having 3 to 18 carbon atoms such as 4-methyl-1-pentene, 1-hexene and 1-octene. Usually the density is in a range of 0.870~0.940g / cm ^3.

The soft polymer comprising an α-olefin copolymer includes, for example, one or more α-olefins selected from ethylene and / or propylene and an α-olefin having 4 to 12 carbon atoms, or a mixture thereof. And a soft copolymer consisting of any combination of
The degree of crystallinity by the line method is generally 30% or less,
This is different from the resin group described above.

The above-mentioned polyolefin has a density of 0.830 to 0.940 g / c in addition to the polymer obtained by the conventional method.
The molecular weight and molecular weight distribution of a polymer, such as a metallocene-based catalyst typified by a single-site catalyst, represented by m ³ , also include those more uniform than conventional ones.

As the ethylene-vinyl acetate copolymer, those having a vinyl acetate group content of 5 to 26% by weight and a melt index (190 ° C., 2.16 kg) of 0.2 to 10 are preferred. Next, as the ethylene-aliphatic unsaturated carboxylic acid copolymer and the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-
Acrylic acid esters (methyl, ethyl, propyl, C ₁ is selected from an alcohol component of -C _8, such as butyl) copolymer, ethylene - methacrylic acid ester (methyl, ethyl, propyl, of C ₁ -C ₈ of butyl (Selected from alcohol components). These may be at least two or more multi-component copolymers in which the components to be copolymerized are selected from the above or other components.

Further, modified polymers of these polymers may be used. Representative examples thereof include ion-crosslinkable copolymers, such as ethylene-methacrylate copolymer and ethylene-acrylate copolymer. At least a part of other suitable copolymer or at least a part of at least a part of the above-mentioned ester derivative saponified is ion-bonded with an ionomer resin or at least one part of a copolymer with the carboxylic acid. Examples thereof include those in which a part is ion-bonded, and those in which at least a part of the carboxylic acid part of the above-mentioned multi-component copolymer is ionized. The polyolefin-based resin constituting the layer (A) is preferably selected from at least one or more of the above-mentioned resins, or as a form of a composition appropriately blended.

Next, the polymer layer (B) of the present invention comprises O ₂ ,
It has a role as a main gas barrier layer for CO ₂ , N _{2 and} other organic gases, etc.
In order to avoid physical property deterioration due to physical and chemical actions such as external force and heat, it is preferable to arrange at least one layer inside.

The layer (B) contains a copolymer having a hydroxymethylene unit obtained by reducing at least a part of the carbonyl group of the polyketone,
Moreover, the polyketone is typically a copolymer of carbon monoxide and at least one α-olefin having 2 or more carbon atoms, or a mixture of carbon monoxide and at least one α-olefin and vinyl acetate, A copolymer with at least one monomer selected from unsaturated carboxylic acids and aliphatic unsaturated carboxylic esters is desirable.

The copolymer having a hydroxymethylene unit constituting the layer (B) may be further saponified,
Alternatively, those obtained by denaturing (chemical reaction such as ionization and grafting) are also included. The polyketone referred to in the present invention refers to carbon monoxide and at least one α-carbon having 2 or more carbon atoms.
Copolymers of olefins or of carbon monoxide with at least one α-olefin and at least one monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid and aliphatic unsaturated carboxylic acid ester It is a copolymer.

The α-olefin having 2 or more carbon atoms includes ethylene, propylene, butene-1, pentene-
In addition to 1,4-methyl-pentene-1, hexene-1, and octene-1, at least one selected from those having up to 12 carbon atoms is usually used. Preferably, ethylene alone or ethylene is used. And propylene in combination,
Or a mixture of ethylene and an α-olefin having 4 to 8 carbon atoms, and further ethylene and propylene and 4 to 8 carbon atoms.
And an α-olefin of No. 8 in combination.

In some cases, monomers such as vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester may improve the flexibility of the polymer after reduction treatment and the adhesion to other substrates. In addition to the improvement of compatibility in blends with other polymers, etc., besides the same improvement as described above by performing a modification treatment such as saponification reaction, graft treatment, ionomerization before and after the reduction treatment, a gas barrier It is useful for strengthening / controlling properties and improving toughness, etc., and is used in an appropriate amount according to the purpose.

The method for producing the polyketone is a known method, for example, as described in US Pat. Nos. 2,495,286 and 4,473,482, JP-B-47-3733, and JP-A-53-473. 128690, JP-A-62-2
53332, JP-A No. 1-132629, JP-A No. 1-201333, JP-Journal of candy <br/> States emissions Chemical Society (1982), No. 104
Vol., Pp. 3520-3522, and is not particularly limited thereto.

The weight average molecular weight of the commonly used polyketone is 4,000 to 1,000,000, preferably 5,
000 to 500,000. The solution viscosity ( η _{SP / C} ) using m-cresol at 60 ° C. after hydrogenation described below corresponds to about 0.5 to 5.0. No particular limitation For a repetitive alternating units of carbon monoxide units and α- olefin units are bound,
From the viewpoint of gas barrier properties, those containing a highly repetitive (alternating) portion are preferred.

Next, the carbonyl group [> C = O] in the above polyketone is reduced to give a hydroxymethylene unit [-C
As a method for obtaining a copolymer containing H (OH)-], any method including a known method can be used, including a reaction in which a carbonyl group in a polyketone is finally converted to hydroxymethylene by hydrogenation. good.

At this time, pure water finally converted into hydroxymethylene units, excluding carbonyl groups remaining unreacted, or those subjected to an ether bond, deOH reaction or partial cross-linking reaction by a side reaction, etc. The conversion ratio (hereinafter simply referred to as hydrogenation conversion ratio) is at least 50%, preferably 70% or more, more preferably 80% or more, further preferably 90% or more, and most preferably 95% or more. If the hydrogenation conversion is less than the above lower limit, it is difficult to exhibit gas barrier properties.

The copolymer has a hydroxymethylene unit content obtained by the above reduction of 10 to 50 mol%, α
-The total of the olefin units is in the range of 40 to 90 mol%, and the other residues are in the range of 0 to 30 mol%. When the content of the hydroxymethylene unit is less than 10 mol%, the gas barrier property is poor, and the upper limit is 50 mol% due to structural restrictions of the raw material polyketone of the present invention. The hydroxymethylene unit content is preferably from 20 to 5
0 mol%, more preferably 30 to 50 mol%, still more preferably 40 to 50 mol% (however, if necessary, the group derived from the vinyl ester (vinyl alcohol) formed is not included in this group, and Base.)

The layer (B) may be formed of a mixed system of the copolymer and another resin. In this case, the proportion of the copolymer is 10% by weight or more, preferably 50% by weight. %, More preferably 70% by weight or more.
(B) As a resin which may be blended with the base resin of the layer,
Resins having known gas barrier properties (eg, polyamide-based polymers, polyester-based polymers, ethylene-vinyl alcohol-based copolymers, and the like, Polymer, ethylene-vinyl alcohol copolymer), or other ethylene-rich materials (ethylene content: about 55
~ 80 mol%) ethylene-vinyl alcohol copolymers, partially saponified products thereof, or modified products thereof,

The polyolefin resin, the ionomer resin, the styrene-conjugated diene block copolymer used in the layer (A), and a polymer obtained by hydrogenating at least a part of the block copolymer. Is modified, for example, grafted with a monomer having a carboxylic acid group as a polar functional group, or polyketones according to the present invention, a polymer mainly formed by side reactions during hydrogenation of polyketones, crystals 1,2-polybutadiene and the like, and at least one selected from these. It is also preferable to use at least one polymer selected from an ethylene-vinyl alcohol copolymer, a polyamide polymer, an ionomer polymer and the like.

In the layer (B), the ratio of the copolymer is 50%.
When the amount is less than 10% by weight, it is preferable to use the mixture with the above-mentioned resin having a known gas barrier property. In this case, the ratio of the known barrier resin to the polymer in the entire layer (B) of the blend is used. Is more preferably 50% by weight or more.

The barrier property of the layer (B) is preferably about 300 cc [25.4 μ / m ² · 2 in terms of oxygen permeability.
4 hr · atm (25 ° C., 65% RH)], but more preferably 150 cc [25.
4μ / m ²・ 24hr ・ atm (25 ° C, 65% R
H)].

The film of the present invention comprises at least one polymer layer (A) and (B) each.
(A) at least one of the layers is located on the surface, and (B)
Preference is given to a layer arrangement consisting of at least three layers, at least one of which is an internal layer. The meaning of at least three layers naturally includes four layers, five layers, six layers, seven layers, and more. Here, the layer (A) or the layer (B) is 2
In the case of a composite film having more than one layer, the resins constituting those layers may be the same or different.

Further, if necessary, an intermediate layer (C) composed of a different polymer may be added between the (A) layer and the (B) layer depending on the use conditions. The intermediate layer (C) comprises at least one of an adhesive layer for increasing the adhesive strength between the two layers, or at least one of the resins (A) and (B) for reusing scraps and the like of the film of the present invention. It is also effective as a collection layer including a part.

Examples of the resin used as the former adhesive layer include ethylene-vinyl acetate copolymer and ethylene-vinyl acetate.
Aliphatic unsaturated carboxylic acid copolymers, ethylene-aliphatic unsaturated carboxylic acid ester copolymers, or multicomponent copolymers composed of at least two kinds of optional combinations of ethylene and the above copolymerizable monomers. Or partially saponified ethylene-vinyl acetate copolymer, ethylene-carbon monoxide-
There are a vinyl acetate copolymer, a thermoplastic polyurethane, a known acid-modified polyolefin, and the like. A resin having a type and composition different from those of the two layers (A) and (B) and a compound of an arbitrary resin may be used.

Any one of the polymer layers (A), (B) and (C) of the present invention may be a plasticizer, an antioxidant, a surfactant, a colorant,
It may contain an ultraviolet absorber, a lubricant, an inorganic filler and the like.

In order to impart antifogging property, antistatic property, adhesiveness, lubricity, etc. to one or both surfaces of the surface of the film of the present invention, the surface of the film is treated by corona treatment, plasma treatment or the like as a group (1). Modification or group (2) may be a coating treatment with a surfactant, an antifogging agent, an antistatic agent, or the like, or bleeding by adding these alone or in addition to a resin, or group (3) A known adhesive or pressure-sensitive adhesive may be used for the same treatment.

For example, group (2) includes polyhydric alcohol partial fatty acid esters such as sorbitan fatty acid esters, glycerin fatty acid esters, and polyglycerin fatty acid esters;
Ethylene oxide adducts such as polyoxyethylene alkylphenyl ether, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene glycerin fatty acid ester;

Amines and amides such as alkylamines, alkylamides, alkylethanolamines and alkylethanolamides; polyalkylene glycols, granidine derivatives, phosphate-containing anionic activators, sulfonate derivatives, quaternary ammonium salts, pyridinium salts , Imidazoline derivatives, polyvinyl alcohol, acrylic acid-based hydrophilic polymers, polymers having a pyrrolidium ring in the main chain;

Further, a combination of at least one or more of silica sol, alumina sol and the like can be mentioned. or,
Group (3) includes mineral oil, liquid polybutene, fats and oils not included in the former, known plasticizers, and other viscous liquids (100 centipoise or more), and these are used alone or in appropriate combination. You. Further, the above-mentioned treatments or additives of each group may be arbitrarily combined.

A preferred example of the stretched composite film of the present invention has heat shrinkability and is used for packaging. The characteristic is that the heat shrinkage at 130 ° C. has a value of 20% or more in at least one direction of the length and the width,
In order to save energy at the time of heat shrinkage and avoid the danger of thermal damage to the packaged material, it is desirable to have as low a temperature shrinkability as possible. Preferably, the heat shrinkage at 120 ° C. is at least one direction of vertical and horizontal. 20% or more, more preferably 25% or more, still more preferably 30%
It has the above values. In addition, preferably, both directions have the above values.

The composite film of the present invention has a heat shrinkage of 20%
If it is less than 30, the fit after shrinkage will be insufficient, and it will cause wrinkles and lumps after packaging. Further, the film needs to have stability so as not to cause a dimensional change in a distribution process including storage, and the shrinkage onset temperature of the film is desirably 45 ° C or higher, preferably 55 ° C or higher. However, the shrinkage onset temperature of the film refers to the temperature at which the heat shrinkage becomes 5%. An example of the composite film of the present invention is a household wrap (for example, a microwave oven) film having characteristics other than those described above (however, heat shrinkage characteristics).

The film of the present invention has an overall thickness of 5 to 1
The thickness is 00 μm, preferably 6 to 80 μm, and more preferably 7 to 50 μm. When the thickness is less than 5 μm, the film tends to be insufficiently stiff and tends to be torn, which causes a problem in workability at the time of packaging, and the possible thickness of the (B) layer as a main gas barrier layer becomes thin,
Practically hinders.

On the other hand, if it exceeds 100 μm, the film becomes too stiff, and in the case of a heat-shrinkable film, there are problems such as poor fit and sealability. In addition, the responsiveness of shrinkage may be poor, or the overall shrinkage force may be too strong, resulting in impaired finish. However, this is not always the case when using as a sheet or bottle.

The thickness of the layer (B) as a preferred embodiment of the film of the present invention is 0.5 to 20 μm in total, preferably 1.0 to 15 μm. If the thickness is less than 0.5 μm, the probability of generation of pinholes due to foreign substances such as gel may increase, and the quality of gas barrier properties may decrease due to the influence of thickness unevenness. On the other hand, when the thickness is 20 μm or more, the cost is increased and the performance is excessive due to the use of a high-priced resin, and a problem occurs in the stretchability.

The total thickness of the layer (A) is suitably used within the range of 5 to 90% of the total thickness of the film depending on the characteristics of the resin used, and is 2 to 50 μm, preferably 3 to 40 μm.
μm. (However, when the adhesive layer is used as the intermediate total (C), the thickness used is included in the total thickness of the (A) layer.)

When the layer (A) is used as the surface layer, the thickness of the layer (A) forming one surface layer is 1 μm or more, preferably 1.5 μm or more. (A) The lower limit of the total thickness of the layer is necessary for ensuring the effect of exhibiting mechanical strength such as tear strength and the sealing property, and the upper limit is a substantial adverse effect on the stretch film forming property and shrinkability or excessive. Limited to avoid performance.

For a wrap film, a film having a thickness of 5 to 15 μm, preferably 7 to 13 μm as a whole is preferred because of good usability. The film of the invention may have at least one layer cross-linked, in which case
Even if the degree of cross-linking in the thickness direction is almost uniform, even if a specific layer is mainly cross-linked, one surface layer is mainly and gradually changes in the thickness direction, even if both surface layers are main, It may have a timely distribution in the direction.

This cross-linking treatment may be performed before or after stretching film formation by arbitrarily irradiating an energy beam such as an electron beam, an ultraviolet ray, an X-ray, an α-ray, a γ-ray, or a peroxide (or a specific layer, if necessary). (A cross-linking aid may be added to the specific layer, and a cross-linking retarder may be used in the specific layer.) Means electron beam irradiation (for example, 50 to 10
The method of controlling the penetration depth with an energy of 00 kV to a predetermined value) is clean and good.

By the crosslinking treatment, the heat resistance and heat sealing properties, especially the sealing properties in high-speed packaging, are improved, and the stretching film formation stability (suppression of necking, uniformity of thickness, improvement of stretching ratio, expansion of stretching temperature conditions). Etc.) can be improved and used as needed.

Examples of the stretching method include a roll stretching method, a tenter method, and an inflation method (including a double bubble method). There is no particular limitation, but a method in which a film is formed by simultaneous biaxial stretching is preferable. The orientation level of the obtained film is not particularly limited as long as it has been subjected to a stretching treatment. However, in the case of a heat-shrinkable film, a certain degree of orientation is practically required.

As an example of a production method for obtaining such a heat-shrinkable film, first, each layer (the (A), (B) layer and, if necessary, the (C) layer, etc.) of the composite film of the present invention is used. The constituent polymer is melted in each extruder, co-extruded with a multilayer die, quenched and solidified to obtain a raw material of a composite film.

The rapid cooling at the time of co-extrusion is for facilitating subsequent stretch film formation, and is important for imparting effective molecular orientation and achieving uniform thickness. The extrusion method is not particularly limited. For example, a multilayer T-die method, a multilayer circular method, or the like can be used, and the latter is preferable. If necessary, the composite film raw material thus obtained is subjected to a cross-linking treatment by electron beam irradiation, and then stretched under heating at a temperature suitable for imparting orientation.

[0058] heat shrinkage stress of the heat-shrinkable film thus obtained is usually in the range of 40~500g / mm ^2, preferably, 50 to 400 g / mm ^2, more preferably, at 70~300g / mm ² is there. The heat shrinkage stress value may be a part of the heat shrinkage stress value of the shrinkage stress characteristic measured at each temperature at which the heat shrinkage is developed, as long as it falls within the above range. A preferable measurement temperature is appropriately adopted within a range of 60 to 160 ° C.

When the heat shrinkage stress is less than 40 g / mm ^{2, the} effect of modification by stretching (strength, transparency, cutting property, etc.)
Is insufficient, and the fit of the film after shrinkage during shrinkage packaging becomes insufficient, which causes wrinkles and wrinkles after packaging. If it exceeds 500 g / mm ² , the package may be deformed depending on the contents of the package, resulting in impaired appearance,
There is a danger that the seal portion is broken or the film is shifted from the container to be packaged due to heating in the microwave during wrapping.

The stretching ratio is not limited to the case of the heat-shrinkable film.
Stretching is performed at 0 times, preferably 8 to 50 times, and is appropriately selected depending on the application, but biaxial stretching is preferable.

As described above, the composite film of the present invention is excellent in melt processability and stretch film forming property, can be arbitrarily used with an energy beam treatment such as electron beam, and has good mechanical and optical properties. It is a novel gas barrier film with excellent heat sealing properties. This film is mainly suitable for packaging materials, especially shrink wrapping, and is a film that can be used as a wrap film for home use and business use, especially by taking advantage of its excellent gas barrier properties.

Hereinafter, measurement and evaluation methods in the present invention and examples will be described. Heat shrinkage rate A 100 mm square film sample is placed in an air oven type constant temperature bath set at 130 ° C., and treated for 10 minutes in a freely shrinkable state. Then, the shrinkage amount of the film is obtained, and the percentage of the value obtained by dividing by the original dimension It was represented by In the case of uniaxial stretching, the stretching direction,
In the case of biaxial stretching, which is a preferred embodiment, the average in the vertical and horizontal directions was used.

Heat Shrinkage Stress The film was sampled in a strip shape having a width of 10 mm, and the sample was placed on a chuck with a strain gauge for 50 m between the chucks.
m was set without loosening, immersed in silicone oil heated to each temperature, and obtained by detecting the generated stress. When the silicone oil is 80 ° C. or lower, the maximum value within 20 seconds after immersion is used, and when the temperature exceeds 80 ° C., the maximum value within 10 seconds after immersion is adopted.
The average value in the vertical and horizontal directions was used.

The measurement was performed according to HAZE ASTM-D-1003-52. Tear strength Measured according to JIS-P-8116 using a light load tear tester (manufactured by Toyo Seiki). In addition, although reading of each measured value is performed so that it may fall in the range of 20 to 60 on the scale, if there is a difference between the measured values depending on the measurement range, the higher value is adopted.

Heat Seal Strength The film pieces were stacked so that the heat seal layers of the stretched film faced each other, and sealed with an impulse sealer were used as test pieces having a width of 15 mm, and the peel strength was measured with a tensile tester.

O ₂ TR (oxygen permeability) Unit: cc / m ² · 24 hr · atm (23 ° C.) Measured according to the method of ASTM-D-3985. Film-forming stability The continuous film-forming stability (continuous film-forming stability of stretched bubbles) of the film and the thickness unevenness of the completed film were evaluated when the film was heated and stretched by a predetermined method.

Here, the thickness unevenness of the film is measured using a dial gauge at least 25 points at equal intervals in the entire width (width) direction of the film and at least 25 points at 3 cm intervals in the flow (vertical) direction, for a total of 50 points. The above thickness is measured, and the average value is calculated first. Next, 1/2 of the difference between the maximum value and the minimum value
Is expressed as a percentage of the previously calculated average value, and this value is indicated with a plus or minus sign.

A: The stretching start position of the film (stretched bubble) is almost constant, the stretch pattern is extremely stable,
Good continuous stability. ：: Film thickness unevenness is within ± 15%. Δ: The stretching start position fluctuates or the stretching pattern is unstable. ×: Film breakage, bubble puncture frequently occurred. Alternatively, even if stretching can be performed, the stretching start position greatly fluctuates, and the thickness unevenness exceeds ± 25%.

Gel fraction A sample was extracted in boiling p-xylene (12 hours), and the ratio of the insoluble portion was expressed by the following formula, and used as a measure of the degree of crosslinking.

## EQU1 ## Gel fraction (% by weight) = (weight of sample after extraction / weight of sample before extraction) × 100 However, a polymer which is not cross-linked and which is not completely dissolved in boiling p-xylene is The measurement is carried out by appropriately changing to a solvent which can be completely dissolved at the time of boiling instead of p-xylene.

[0070]

The present invention will be described in more detail with reference to the following examples, which do not limit the scope of the present invention. (Example 1) Ethylene-α-olefin copolymer; a ₁
[Comonomer; 4-methyl-pentene-1, density;
910 g / cm ³ , Vicat softening point; 82 ° C., MFR
(190 ° C., 2.16 kg); 3.2] containing 2.0% by weight of an additive having a weight ratio of monoglyceride oleate and diglycerin monolaurate of 1: 1 is used for the surface layer.

Next, a copolymer of ethylene and carbon monoxide, having a number average molecular weight of about 50,000 and a solution viscosity of η _{SP / C} =
1.60 (measured with m-cresol solution at 60 ° C .; the same applies hereinafter), a copolymer containing hydroxymethylene units obtained by hydrogenating a polyketone having a carbonyl group content of 49 mol%; b ₁ [hydroxymethylene unit Is 47 mol% (in this case, the hydrogen conversion rate is 97%), the ethylene unit is 51 mol%, and the other residues are 2 mol%].

Further, as an adhesive layer, an ethylene-vinyl acetate copolymer; a ₂ [vinyl acetate group content: 14% by weight, Vicat softening point: 66 ° C., MFR (190 ° C., 2.16 k
g); 2.5]. Therefore, the layer arrangement is a ₁ / a ₂
/ B ₁ / a ₂ / a ₁ was extruded using an annular multilayer die so as to have five layers, and then quenched and solidified with a refrigerant, and the folding width was 20%.
Each of the layers having a thickness of 0 mm and a thickness of 180 μm was used to prepare a tubular raw material having uniform thickness accuracy.

The thickness of each layer is 54 in order from the outside of the tube.
μ / 27μ / 18μ / 27μ / 54μ. Then, the raw material is passed between two pairs of differential nip rolls, heated to 107 ° C. in a heating zone, and air is injected thereinto in a stretching zone under the same atmosphere to form bubbles, and the stretching ratio is continuously increased. , 3 times in the vertical direction, 3 times in the horizontal direction, biaxially stretched, and cooled by blowing cold air at 20 ° C in the cooling zone.
μ film was obtained.

The stretching stability of the film was good (○), the tear strength was 23 g, the haze value was 1.4%, the heat shrinkage was 47%, the heat shrinkage stress (100 ° C.) was 260 g / mm ² ,
It has physical properties of seal strength 1.5 kg / 15 mm width, and O ₂ TR is 41 cc / m ² · 24 hr ·
Excellent atm and barrier properties, sufficient mechanical strength for practical use,
It was a heat-shrinkable film that retained optical characteristics.

Example 2 Polybutene-1; a ₃ [copolymer with propylene; density: 0.910 g / cm ³ , Vicat softening point: 87 ° C., MFR (190 ° C., 2.16 k
g); a copolymer containing hydroxymethylene units obtained by hydrogenating a surface layer resin with a polyketone having a carbonyl group content of 47 mol% as a core layer resin; b ₂ [39 mol of hydroxymethylene units %, Solution viscosity; η _{SP / C} = 1.
53, ethylene units 47 mol%, propylene units 6 mol%, other residues 8 mol%)], ethylene-methacrylic acid copolymer; a ₄ [methacrylic acid content; 9% by weight, Vicat softening point; 80 ° C., MFR (190 ° C., 2.
16 kg); 3) was disposed in the middle layer,

The layer configuration is five layers of a ₃ / a ₄ / b ₂ / a ₄ / a ₃ , and the thickness is similarly 36 μ / 18 μ / 12 μ / 18 μ.
A total of 120 μ / quenched raw material of / 36 μ was obtained in the same manner as in Example 1 (each surface layer containing the same additives as in Example 1 each containing 2.5% by weight).

The raw material is passed between two pairs of differential nip rolls, heated to 75 ° C. by hot air, stretched as it is in the same manner as in Example 1, and cooled to about 14 ° C. in the cooling zone.
Was blown continuously to obtain a film continuously and stably.
The stretching magnification at this time is 3.4 times the length and 3.5 times the width.
The thickness of the obtained film was about 10 μ. This film has a haze value of 1.0%, a tear strength of 7 g, a heat shrinkage of 43%, a heat shrinkage stress (100 ° C.) of 190 g / mm ² ,
O ₂ TR was 170 cc / m ² · 24 hr · atm.

Comparative Example 1 An ethylene-vinyl alcohol copolymer obtained by saponifying a copolymer of ethylene and vinyl acetate; EVOH-1 [ethylene content: 29 mol%;
Degree of saponification: 99% or more, MFR: 210 ° C., 2.16 k
g) 3.2] copolymers containing hydroxymethylene units obtained by hydrogenating polyketones; was replaced by b ₁ was subjected to co-extrusion stretching under the same conditions as in Example 1.

A bubble puncture sometimes occurred, and the bubble swayed during the stretching and fluctuations in the stretching start position were observed. The stretching ratio was 2.7 times the length and 2.1 times the width. And the stretching film-forming stability was poor. The number of extrusion raw observed diameter less than 1mm in the gel after extrusion after 6 hours was about double in Example 1 and about 24 per ² raw 1 m.

[0080] (Example 3-8) ethylene as two resin for surface layer - copolymers of vinyl acetate; with a _2, a solution viscosity in the core layer resin; η _{SP / C} = 1.65, containing carbonyl groups A copolymer containing hydroxymethylene units obtained by hydrogenating a polyketone having a ratio of 48 mol%; b ₃ (46 mol% of hydroxymethylene units, 52 mol% of ethylene units, and 2 mol% of other residues); Are melted by an extruder, extruded using an annular multilayer die (three layers), quenched and solidified with cold water, and the layer configuration is a ₂ / b ₃ / a ₂ = 250 μ / 100
A tubular raw material of μ / 250μ was prepared. At this time, 3% by weight of diglycerin monooleate as a surfactant was injected and mixed into the cylinder of the extruder with respect to the surface layer.

This tubular raw material was flattened and crosslinked by an electron beam irradiation device (500 kV) so that the gel fractions of both surface layers were equal to about 25%, and stretched in the same manner as in Example 1. . The film was stretched at a heating stretching temperature of 123 ° C., a stretching ratio of 7 times and a width of 5.7 times to obtain a film having a thickness of 15 μm. This was designated as Example 3.

As shown in Tables 1 and 2, a crosslinked stretched film was obtained by changing the layer constitution (the number of layers, resin composition, thickness ratio, etc.) in various ways and using corresponding extruders and multilayer dies in the same manner. . This was made into Examples 4-8.

[0083]

[Table 1]

A ₅ : ethylene-α-olefin copolymer (comonomer; 1-octene, density: 0.930 g / c
m ³ , MFR; 3.0) a ₆ ; ethylene-vinyl acetate copolymer (vinyl acetate content 18% by weight, MFR: 3.5) b ₄ ; solution viscosity η _{SP / C} = 1.75, carbonyl group-containing Hydrogenated polyketone with a ratio of 47 mol% (hydroxymethylene unit 40 mol%, ethylene unit 50 mol%, propylene unit 3 mol%, other residues 7 mol%)

B ₁₁ ; Blend (b ₁ : 70% by weight + E
VOH-2: 30% by weight) EVOH-2; ethylene-vinyl alcohol copolymer [ethylene content: 44 mol%, saponification degree: 99% or more;
MFR (210 ° C., 2.16 kg); 4]

[0086]

[Table 2]

A ₁₂ ; Blend (a ₁ : 60 wt% + a ₂ : 40 wt%) b ₂₁ ; Blend (b ₂ : 30 wt% + Ny: 50 wt% + Io: 20 wt%) Ny: Copolymer nylon 6-66 (nylon 66 content: 1
5% by weight) Io; partially saponified ethylene-methyl methacrylate copolymer cross-linked with Na ions (methacrylic acid and ester group content: 7 mol%, MFR: 1)

The thickness of the raw material was the same as that of Example 3, ie, 60%.
0 μ, the heating and stretching temperature was in the range of 120 to 140 ° C., and the stretching ratio (length × width) was 7 × 5.7, 5.7 × 4.2, and 7. 8 × 6.4 times,
6.times.5 times and 6.times.5 times. These films were excellent in stretching film-forming stability and excellent in various packaging suitability such as shrink wrapping.

As a comparison, a commercially available heat-shrinkable symmetrical five-layer structure in which an ethylene-vinyl alcohol copolymer is disposed in the core layer as a barrier resin, linear low-density polyethylene is disposed on the surface layer, and both are bonded by an adhesive resin. Composite cross-linked film (thickness 2
When 5 μ) was similarly heat-shrinked, a phenomenon in which the core layer was bent and whitened was observed. On the other hand, the film of the present invention did not have such a phenomenon even after heat shrinkage, and was excellent in optical characteristics.

(Examples 9 and 10) In the extruded tubular raw materials obtained in Examples 3 and 4, the cross-linking level by the electron beam irradiation (gel The irradiation was performed by adjusting the accelerating voltage so that the fractions differed.
Stretch film formation was performed under the same conditions as described above.

A case of a film obtained under the same raw material and the same stretching conditions as in Example 3 was referred to as Example 9, and a case corresponding to Example 4 was referred to as Example 10. The gel fraction of each surface layer in Example 9 was 37% outside the tube and 12% inside the tube.
Met. Similarly, in Example 10, the outside of the tube was 26% and the inside was 2%.

Each of the stretched films was stable as in Examples 3 and 4 (（to ◎), and had excellent heat shrinkage (heat shrinkage was 52% in Example 9 and 52% in Example 19). 59
%), Particularly when the packaging speed is increased when the surface layer having a lower crosslinking level is used as a heat sealing layer and the side in contact with the seal bar is used as a high crosslinking layer for packaging. Troubles such as tears and wrinkles at the seal part were eliminated, and high-speed packaging workability was significantly improved.

(Example 11) The molecular weight distribution obtained by polymerizing with a metallocene catalyst on the surface layer was sharp (Mw / M
n = 1.6) ethylene-α-olefin copolymer; a ₇
(Komorimer; 1-octene, density: 0.890 g / c
m _3, MFR; 2.6), polyketone hydrogenated resin as the core layer resin; b _1, acid-modified EV grafted processed adhesive layer
A; Using a ₈ (MFR; 2.8), the layer arrangement is a ₇ /
created in _{a 8 / b 1 / a 8} / a 7 5 -layer structure of the tubular raw sheet of the same manner as in Example 1, and was subjected to the same stretching film formation below.

The thickness of each layer of the tubular raw material was adjusted in the same manner as in Example 1, and the same additive was added to the surface layer in substantially the same amount. The stretching conditions at this time were a heating stretching temperature of 110 ° C., a stretching ratio of 3.6 times and a width of 3.1 times, and a thickness of the obtained film of 16 μm.

The stretching film forming stability was good (○), the tear strength was 16 g, the haze value was 1.1%, the heat shrinkage was 56%, the heat shrinkage stress (100 ° C.) was 215 g / mm ² , and the seal strength was 1. 2 kg / 15 mm width, and O ₂ TR 55 cc / m
Transparency like ² · 24hr · atm, was barrier film having excellent heat shrinkability in the sealing strength and the like.

(Example 12) Using the extruded tubular raw material obtained in Example 5, electron beam irradiation was performed at an accelerating voltage of 200 kV, the gel fraction of one surface layer was 25%, and the other surface layer was Was carried out so that the gel fraction of the sample became 0%.
The raw film was formed into a film under the same stretching conditions as in Example 5 to stably obtain a film having a thickness of 25 μm.

This film had a heat shrinkage of 49%, heat shrinkage stress (100 ° C.) of 125 g / mm ² , and O ₂ TR290c.
The film had physical properties of c / m ² · 24 hr · atm. Like the films obtained in Examples 9 and 10, the film had excellent sealing properties and good suitability for high-speed packaging.

Example 13 A tube-shaped raw material was produced under the same conditions as in Example 1, except that the thickness of each layer (the same applies to the raw material thickness) and the additives for the surface layer were changed. As an additive used, glycerin diacetmonolaurate was added at 2% by weight based on the surface layer. The thickness of each layer of the raw material was 90 μ / 54 μ / 72 μ / 54 μ / 9 in order from the outside of the tube.
It was 0μ.

The obtained raw material was cross-linked with an electron beam (500 kV) to adjust the gel fraction to about 35%. Similarly, a film was formed at a heating stretching temperature of 155 ° C. and a stretching ratio of 6 times each in the vertical and horizontal directions. And a film having a thickness of 10 μm was obtained stably. The heat shrinkage of this film was at a level of 13%. When the suitability of this film as a wrap film was evaluated, cutting using a saw blade cutter (a box for Saran wrap R manufactured by Asahi Kasei Kogyo Co., Ltd.) was performed. Excellent in adhesiveness when wrapping wraps using setware and glass containers.Furthermore, the film turns over even when heated in a microwave oven with wrapped pork belly, causing holes and whitening due to melting. And the microwave oven suitability was also good.

Example 14 A terpolymer (39 mol% carbonyl group content) of ethylene, carbon monoxide and vinyl acetate (3 mol%) was hydrogenated (hydrogen conversion: 96%).
%), A tube-shaped raw material was prepared under the same conditions as in Example 1 except that a gas barrier resin obtained by further saponifying a vinyl acetate group was used as a core layer, and stretched film formation was performed.

However, in addition to adding the same additives to the surface layer, when preparing a tubular raw material, diglycerin oleate was sealed in the tube and the inner surface was coated with a nip roll to perform an inner surface coating treatment. The stretch film forming property was good (（), the tear strength was 27 g, and the haze value was 1.2.
%, Heat shrinkage 44%, heat shrinkage stress (100 ° C) 245
g / mm ² , seal strength 1.3 kg / 15 mm width, and O ₂ TR 51 cc / m ² · 24 hr · atm.

(Example 15) Polypropylene resin [ethylene content: 4.5 mol%, MFR (230 ° C, 2.
16 kg); 4] was used for the surface layer, and a tubular raw material was produced under the same conditions as in Example 1, and stretched film formation was performed.
However, when producing the tubular raw material, diglycerin oleate was sealed inside the tube, and the inner surface was coated by wiping with a nip roll.

The stretch film forming property was stable (◎), the heat shrinkage was 49%, and the heat shrinkage stress (100 ° C.) was 270 g / mm ^2.
Was excellent in heat shrinkability.

[0101]

Industrial Applicability The present invention is a novel gas barrier film which has no problem in environmental hygiene, is excellent in melt processability and stretch film forming property, and is also excellent in mechanical properties, optical properties and heat sealability. It is suitably used for various packaging applications.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (7)

(57) [Claims] A composite stretched film comprising a layer (A) composed of a polymer mainly composed of a polyolefin resin and a layer (B) containing a copolymer having a hydroxymethylene unit as a component, and B) The hydroxymethylene unit in the copolymer constituting the layer is obtained by reducing at least a part of the carbonyl group of the polyketone, and the polyketone has carbon monoxide and at least one carbon number. A copolymer with two or more α-olefins,
Alternatively, it may be a copolymer of carbon monoxide, at least one α-olefin, and at least one monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester. Characterized by a composite stretched film. 2. The polyolefin-based resin comprises a polypropylene-based polymer, a poly-4-methylpentene-based polymer, a polybutene-based polymer, a polyethylene-based polymer, an ethylene-α-olefin copolymer, and an α-olefin copolymer. Flexible polymer, ethylene-vinyl acetate copolymer, ethylene-
Aliphatic unsaturated carboxylic acid copolymers, ethylene-aliphatic unsaturated carboxylic acid ester copolymers, or copolymers of two or more freely selected from the monomers of the above copolymers, or these The composite stretched film according to claim 1, wherein the composite stretched film is at least one selected from a modified polymer of a polymer. 3. The composite stretched film according to claim 1, further comprising an intermediate layer (C) composed of a polymer different from the layers (A) and (B). 4. The composition according to claim 1, wherein the proportion of the copolymer contained in the layer (B) is 10 to 100% by weight.
9. The composite stretched film according to the above item. 5. The method according to claim 1, wherein the content of hydroxymethylene units obtained by reducing the polyketone constituting the copolymer contained in the layer (B) is from 10 to 50 mol%. 5. The composite stretched film according to any one of items 4. 6. The stretched composite film according to claim 1, wherein the hydrogenation conversion of the copolymer contained in the layer (B) is at least 50%. 7. The composite stretched film according to claim 1, wherein at least one layer of the film is crosslinked.