DE2606194C3 - Biaxially stretched tubular multilayer film with gas barrier properties - Google Patents

Description

The invention relates to a stretched, tubular, multilayer film with gas barrier properties (e.g. Impermeability to oxygen).

Furthermore, the film according to the invention is characterized by low extractivity, i. H. low leachability and excellent properties in terms of Heat shrinkage and cold resistance.

When vinylidene chloride copolymer resin containing little or no plasticizer, a simultaneous biaxial orientation by means of the inflation or Is subjected to the expansion process, it is generally difficult to make the resin into one because of the poor sheet compressibility of the resin to form tubular film. Even in the case where a biaxially stretched tubular Film is obtained, the film obtained is poor in cold resistance, and therefore a such film cannot be put to the usual practical use. For this reason, it is customary to produce a biaxially stretched tubular film made of a single layer Vinylidene chloride copolymer resin by means of the inflation or expansion method, a plasticizer and a Stabilizer in an amount of a few percent based on the amount of resin to the resin added. A biaxially stretched tubular However, film obtained from the vinylidene chloride copolymer resin thus plasticized has the The disadvantage that when wrapping food or the like in the film, the plasticizer used diffuses through the film and out of the Slide is excreted and put into the slide

ίο penetrates wrapped food or the like

Therefore, various processes for the production of biaxially stretched films are already under Use of vinylidene chloride copolymer resins, that contain little or no plasticizer, known To z. B. to improve cold resistance, which is deteriorated by the use of vinylidene chloride copolymer resin, and at the same time at the same time of forming a tubular film is good To maintain film compressibility, a simultaneous biaxial orientation process has been developed which laminating the vinylidene chloride copolymer resin and the other thermoplastic resin and thereon subsequent inflation or expansion of the laminated The simultaneous biaxial orientation process can e.g. B. be carried out in that simultaneously the above-mentioned vinylidene chloride copolymer resin and polyolefin or olefin copolymer resin using an annular shape or Nozzle can be extruded together in such a way that both resins can be laminated, the obtained two-layer tubular product at a certain length with two pairs of clamping or Holding rollers is clamped in the longitudinal direction (where

r »a gas within the tubular product that is curled between the two pairs of pinch rollers is, is trapped and the pressure of the gas inflates or expands the tubular product and so on the so-called bubbles) and then the hose shaped product run successively and at the same time the tubular product clamped between the two pairs of pinch rollers heated so that it can be stretched. By controlling the respective speed of rotation

«The two pairs of pinch rollers or by control the pressure of the gas trapped within the tubular product clamped between the two pairs of pinch rollers, can biaxially stretched two-layer hose form moderate foils with different orientation ratio sen are preserved.

However, in the case that the vinylidene chloride copolymer resin and polyolefin are such as uncrosslinked polyethylene low density laminated and the simultaneous biaxial subject to orientation according to the procedure it is difficult to obtain a tubular film with an orientation ratio of 2.5 to 5 times each in the longitudinal and transverse directions as it is for the increase in mechanical strength such as

W) For example, resistance to cold is necessary. To a To achieve such an orientation ratio using the polyethylene, it is therefore necessary to di * Crosslinking of the polyethylene by irradiation, e.g. B. with electromagnetic radiation or electrons radiate, to improve the polyethylene before that Stretching is performed. However, as is well known, the irradiated polyethylene has the disadvantage on that, although the polyethylene at the time of the biaxial

Orientation has good processing characteristics, which by the irradiation between the Polymers caused crosslinking bonds and worsen the thermo-plasticity of polyethylene hence a process for the production of tubular films using polyethylene very gets complicated. That means that a method for Irradiating a tubular product with electromagnetic rays or electron beams must be interposed between the process of extruding the resins and the process of stretching the product. In addition, in the event that a biaxially stretched tubular film is made which is composed of a layer of vinylidene chloride copolymer resin and two layers of polyethylene is the lamination of the polyethylene layers according to the Irradiation of the polyethylene with electromagnetic rays or electron beams are carried out, as described in US Pat. No. 3,741,253, for example

When the vinylidene chloride copolymer resin and olefin copolymer such as. B. ethylene vinyl acetate copolymer laminated and a simultaneous biaxial orientation according to the method described above are subjected to, the stretching can hardly be carried out up to a ratio of 2.5 to 5 times each in the longitudinal and transverse directions when 30% or more of the wall thickness of a two-day tubular product that is produced by simultaneously extruding the two copolymers has been obtained from an annular nozzle, is occupied by the ethylene vinyl acetate copolymer and when the wall thickness of the tubular product is small (e.g. about 100 μ) and the folding width thereof is large (e.g., 200 mm or more). When the wall thickness of the tubular Product is large (e.g. 500μ or more) and the folding width of the same is small, the internal pressure becomes of the above-described bubbles high when performing the orientation on the tubular product. Therefore, the orientation becomes uneven, or the shoulder parts of the bubbles become inclined to Breakage or tearing, so that a high ratio of orientation cannot be achieved. In summary, this means when the tubular product having a large wall thickness and a small fold width as mentioned above is what is obtained Orientation ratio about at most 1.7 times (short: 1.7) which is half or less of that common orientation ratio obtained when vinylidene chloride copolymer resin is used alone. Accordingly, it makes it one of those low orientation ratio impossible, the mechanical strength of the obtained biaxially stretched to improve tubular film. Furthermore, when using such an ethylene vinyl acetate copolymer, as mentioned above, it is difficult to obtain that of one annular nozzle or shape to subject extruded tubular product to orientation, regardless of the wall thickness and fold width thereof, if the proportion is in the copolymer polymerized vinyl acetate is small

On the other hand, from DE-OS 19 32 934 a multilayer packaging film is known in which a Layer made of a thermoplastic polymer material and another layer connected to it cured vinylidene chloride copolymer of a certain composition. Since polyolefin films are known to show poor adhesion, This special layer structure was intended to create an improved bond between the individual film layers while maintaining a good gas barrier effect. However, the bond between the s individual layers are still unsatisfactory, especially with regard to difficulties with the Orientation process step

It is therefore an object of the present invention to provide a biaxially stretched tubular multilayer film

ι ο to create that using a little or nothing vinylidene chloride copolymers containing no plasticizer and improved bonding to the base layer made of a polyolefin material

This object is achieved in the case of the film described in that it 1. comprises a gas barrier layer Contains vinylidene chloride copolymer, which consists of 65 to 95% by weight of vinylidene chloride and 35 to 5% by weight of one or more unsaturated compounds with the vinylidene chloride copolymerizable monomers has been prepared and 2. one or more cold-resistant, i.e. under Layers of polyolefin or a mixture of polyolefin (homopolymer) and olefin copolymer, which are firmly adhering, retain their properties in the cold attached to the gas barrier layer; and further that at least one of the cold-resistant Layers contains an ionomer and that the thickness of the gas barrier layer 3 to 70%, based on the total thickness of these layers, and the thickness of one or

jo several of the cold-resistant layers at least 5%, based on the total thickness of these layers, and also the total volume of the in one or several of the cold-resistant layers contained ionomer 4 to 85%, based on the total volume

j5 of these layers is

The inventors found that the resulting film had excellent physical properties such as z. B. Heat shrinkage, gas barrier property and cold resistance has the same or better than that a biaxially stretched tubular film obtained from the usual plasticized vinylidene chloride copolymer resin, and which are also a Has an orientation ratio of 2.5 to 5 times in each case in the longitudinal and transverse directions when vinylidene chloride copolymer and olefin copolymer laminated and the resulting laminate of a simultaneous biaxial orientation by the inflation or Is subjected to expansion processes and if further an ionomer or a mixture of ionomer and polyolefin (homopolymer) is incorporated into the olefin copolymer. With regard to the ionomer, on page 7.2. Referenced paragraph.

In particular, by incorporating the ionomer, the adhesion between the layer of the Vinylidene chloride copolymer and the layer of olefin copolymer or a resin mixture of polyolefin and Olefin copolymer improved quite outstandingly.

On the basis of these findings, the present invention has been completed. According to the present

bo lowing invention a biaxially stretched tubular two-layer film is created, which consists of a Layer of vinylidene chloride copolymer and a layer of olefin copolymer containing an ionomer, or a layer of olefin copolymer, the polyolefin

Contains M (homopolymer) and ionomer is. Furthermore, the present invention provides a biaxially stretched tubular three-layer film created, which consists of a layer of vinylidene chloride

Copolymer and two layers composed of olefin copolymer or a resin mixture of polyolefin (homopolymer) and olefin copolymer, each of which are adhered to the upper surface and the lower surface of the vinylidene chloride copolymer layer, wherein either or both of the latter two layers contain an ionomer.

The vinylidene chloride copolymer for use in the present invention is a copolymer composed of 65 to 95 wt .-% vinylidene chloride and 35 to 5 wt .-% of at least one of the unsaturated monomers with are copolymerizable with vinylidene chloride, the monomers include e.g. B. a: vinyl chloride, Acrylonitrile, alkyl ester acrylate (the alkyl group has 1 up to 18 carbon atoms), alkyl ester methacrylate (the Alkyl group has 1 to 18 carbon atoms), butadiene, styrene, vinyl acetate, ethylene, propylene, isobutylene, vinyl alkyl ketone (the alkyl group has 1 to 18 Carbon atoms) and alkyl vinyl ethers (the alkyl group has 1 to 18 carbon atoms). The vinylidene chloride copolymer can, if necessary, with 0.5 to 15 parts by weight of a plasticizer and a stabilizer are mixed. For these plasticizers and the stabilizers can be mentioned, for example: adipic acid dioctyl ester, sebacic acid dioctyl ester, sebacic acid dibutyl ester, polyvalent hydroxy ester carboxylates such as tributyl citrate and tributyl acetyl citrate, glycerol esters, polyester plasticizers, epoxidized vegetable oils, epoxy octyl stearate isopropyl denaturing agents such as diphenolepichlorohydrin condensate

The ionomers for use in the present invention are ionic copolymers having ionic crosslinking bonds, and more particularly the copolymers obtained by having a copolymer consisting of alpha-olefin such as ethylene and propylene and an unsaturated organic acid such as acrylic acid and methacrylic acid with metal ions such as Na ⁺ , K ⁺ , Ag ⁺ , Cu ²⁺ , Ca ²⁺ , Ba ²⁺ , Zn ²⁺ and Fe ^{2+ has} been brought to crosslink. These ionomers are known to those skilled in the art

The olefin copolymer is required to be somewhat adhesive to the vinylidene chloride copolymer at the time of use. For this purpose, the olefin copolymer used for the invention is a copolymer composed of olefin and vinyl ionomer having a carboxylic acid group in its molecule such as B. ethylene-vinyl acetate copolymer. The olefin copolymer is used alone or it is a resin mixture consisting of olefin copolymer and polyolefin (homopolymer), such as. B. polyethylene is used. In this case, it must be noted that if the crystalline melting point of the copolymer or the resin mixture is 20 ° C or more above that of the ionomer, then the heating temperature at the time of orientation becomes so high that the ionomer at the time of orientation becomes complete molten state comes and therefore no effect of the use of the ionomer t> o is developed at all. On the other hand, if the crystalline melting point of the copolymer or the resin mixture is too low, the end product becomes the tubular multilayer film, poor in heat resistance. For this reason, a preferred μ crystalline melting point 6O ⁰ C or more. Accordingly, the peak value of the crystalline melting point of the olefin copolymer or the resin mixture is a measurement using the differential Abtastcalorimeters (differential scanning calorimeter of DSC IB type, manufactured by Parking-Elmer Corporation) at 110 ° C ODTR lower, preferably within the range from 6O ⁰ C to 110 ° C More specifically, the measurement of the crystalline melting point under such conditions carried out that 8 mg of the test sample and a heating rate of 8 ° C per minute are used. The maximum peak value of the obtained crystal melting curve is regarded as the crystal melting point. As an olefin copolymer having such characteristics, there can be mentioned, for example, ethylene-vinyl acetate copolymer composed of 5 to 30% by weight of vinyl acetate and 95 to 70% by weight of ethylene

The biaxially stretched tubular multilayer film according to the invention is a biaxially stretched one tubular two-layer film (hereinafter referred to as film A), which consists of a layer of the Vinylidene chloride copolymer (hereinafter referred to as the layer I) and a layer of olefin copolymer or a resin mixture of polyolefin and Olefin copolymer (hereinafter referred to as the layer H) is further composed biaxially stretched tubular multilayer film according to the invention a biaxially stretched tubular three-layer film (hereinafter referred to as film B called) of the so-called sandwich type, which consists of layer II, layer I, which is at the bottom Surface of the layer II is adhered and the further layer II, which is attached to the lower surface the layer I is adhesively attached is composed. The layer II in the film A necessarily contains a Ionomer. At least one of the two layers that made up the layer II exist, in the film B also necessarily contains an ionomer. The thickness of the layer I in the Films A and B must each be 3 to 70%, preferably 5 to 50%, based on the thickness of the film. In fact because each of the thicknesses of the films A and B is considered to be in the range of e.g. B. 10 to 200 μ viewed lying what is the thickness of the film for use in food wrapping; the gas barrier property (e.g., the oxygen permeability barrier property) is extremely deteriorated when the Thickness of layer I is less than 3% of the thickness of the film, whereas the cold resistance of the film is somewhat becomes smaller when the thickness of the layer I exceeds 50% of the thickness of the film, and the film is insufficient in terms of their mechanical strength when the thickness of layer I exceeds 70%, thus rendering the film unusable for practical purposes. Furthermore, it is necessary for the film B that the two layers of Layer II each have a thickness of 5% or more of the thickness of the film. In fact because if either of the two layers of layer II has a thickness less than 5%, then the layer II of the film B, if this is used, is not effective as a protective layer against mechanical stresses such as e.g. B. by shock and External friction acts

The amount of ionomer to be incorporated into layer II of film A is 4 to 85% by volume Slide A. The amount of ionomer present in at least one of the two layers of the layer material II of the Foil B is also to be incorporated is 4 to 85% by volume of foil B. The only thing that needs to be done for the film to contain the ionomer is to add the ionomer with the olefin copolymer or resin blend

Mix. As mentioned above, by using the olefin copolymer or the Resin mixture made possible to increase the adhesiveness between the layer I and the layer II. Also, the use of ionomer provides stability for the formation of the bubbles at the time of orientation and errr.rigücru it like that. the orientation uniform with a high orientation ratio and enables simultaneous lamination of the Layer I and Layer II by the usual coextrusion process.

Films A and B of the invention can be made by conventional inflation or expansion processes will. According to the method, a biaxially stretched tubular multilayer film can also be used Layers that are fused and bonded together evenly with an orientation ratio from 2.5 to 5 in the longitudinal direction and the transverse direction, respectively. The manufacture of the tubular multilayer films according to the method has the advantage that the construction of the production apparatus is simple and enables stable operation because no auxiliary equipment is used in the process become, such as B. an irradiation apparatus to achieve crosslinking in the conventional Method using polyethylene is used.

When using the biaxially stretched tubular multilayer film of the present invention In the invention, layer I plays the role of a gas barrier (e.g. a barrier against oxygen permeability) and the layer II acts as a cold-resistant property retaining one Layer or as a heat seal layer. Therefore, the present film is suitable and practical for Use when wrapping food. Furthermore, the film according to the invention has a high

(3) Polyolefin Copoiymer and Polyolefin:

Young's modulus (i.e., the film has stiffness) as compared to the films which pass through the known processes can be obtained due to the fact that they contain an ionomer so that it is advantageous in handling when it is processed.

The invention will now be explained in detail by means of examples. However, you are not supposed to focus on this Examples will be limited.

The polymers used in these examples are as shown below.

(1) vinylidene chloride copolymer:

symbol

A vinylidene chloride / vinyl chloride = 71/29

(Copolymer) 100 parts by weight,
epoxidized bean oil 1 part by weight.

B vinylidene chloride / vinyl chloride = 80/20

(Copolymer) 100 parts by weight,
epoxidized bean oil, 1 part by weight
Adipic acid dioctyl ester 0.4 parts by weight.

C vinylidene chloride / vinyl chloride /

Lauryl acrylate = 85/15 / 6.5 (copolymer)
100 parts by weight

(2) ionomer:

Icon ion melt index density crystal

melting point

Degrees / min (g / crn ^) ( ⁰ C)

N / A
N / A

0.9 1.2

0.94
0.94

87
95

The monomer units of the two ionomers D and E are "ethylene" and "methacrylic acid".

symbol Type of polymer Melt index density crystal
melting point
( ⁰ C) Remarks (Degrees / min) (g / cm *) 105 F. Low density polyethylene 2.0 0.921 98 G Ethylene vinyl acetate copolymer 1.5 0.927 91 5% by weight vinyl acetate H Ethylene vinyl acetate copolymer 1.5 0.93 95 10% by weight vinyl acetate 1 the same 0.5 0.93 87 the same J the same 0.6 0.93 87 15% by weight vinyl acetate K Ethylene-acrylic acid copolymer 1.5 0.925 7% by weight acrylic acid

example 1

Vinylidene chloride copolymer (A) was used as the skin resin and a mixture containing obtained by mixing the ionomer (D) and olefin copolymer (J) in a mixing ratio of 1: 1 was used as the inner layer resin using two extruders and ring-shaped Nozzles, these resins were molded and coextruded in two layers inside the dies to obtain a tubular product.

The diameter of each nozzle was 60 mm, the width of the nozzle gap was 13 mm, the nozzle edge was 13 mm, and the resin temperature at the nozzle edge was 168 ° C. The thickness ratio of the inner layer to the outer layer was 7: 3. Accordingly, the ionomer content was about 35% in terms of volume ratio. Thereafter, the hose conveyor obtained was

«Mige product cooled in a water bath at 15 ° C and, while being pulled with a squeegee roller in the water bath, the product became so shaped to have a thickness of 450 µm and a flat width of 95 mm. The inside of the tubular

The product in the water bath was mixed with propylene glycol filled to a level almost equal to the surface of the water bath to reflect the shape of the To hold the product and at the same time to prevent the inner surfaces of the product from melting

join hj zen together. Then the tubular product heated in a hot water bath to 83 ° C, which temperature is lower than that The melting point of the olefin copolymer (J) is, and

while using the product of a longitudinal orientation with an orientation ratio of 3.0 was subjected to a pair of nip rollers, a simultaneous biaxial orientation on the Product carried out on the hot water bath using air. As a result, the Shoulder position of the bubbles on the hot water bath and the orientation ratio with a transverse orientation ratio stabilized from 3.0.

Example 2
(Comparative example)

Olefin copolymer (J) was used as the inner layer resin ι ^r> and vinylidene chloride copolymer (A) as the core layer resin and olefin copolymer (J) as the outer layer resin. Using three extruders and annular dies, these resins were molded in three layers inside the dies and coextruded to obtain a tubular product. The diameter of each nozzle was 90 mm, mm, the width of the die gap 1.5 and the resin temperature at the nozzle edge was 165 ° C. The thickness ratio of the three-layer tubular product 2 ^r> was adjusted by the extrusion amount of each extruder, and the thickness ratio of the outer layer to the core layer to the inner layer was 1: 3: 1. Then, the tubular product was cooled in a water bath at 30 ° C, and Mt was pulled at an opening provided in the water bath squeeze roll during the product, it was formed so as to μ a thickness of 600 and a flat width of 130 mm having . The inside of the tubular product in the water bath was filled with propylene glycol to a level almost equal to the surface area of the water bath in order to maintain the shape of the product while preventing the internal surfaces of the product from being melted together. The tubular product was then heated to 87 ° C. in a hot water bath, which temperature was lower than the melting point of the olefin copolymer (J). While the tubular product was subjected to longitudinal orientation with an orientation ratio of 3.1 using a pair of nip rollers, simultaneous biaxial orientation was carried out on the product on the hot water bath using air pressure, however, since the shape of the bubbles did not take a definite shape and the bubbles tended to break or crack, transverse orientation with an orientation ratio of 3 or more could not be carried out as intended.

Example 3

Biaxial orientation was carried out under the same conditions used in Example 2 performed with the exception that the outer layer- t> o resin of Example 2 has been replaced by a mixture obtained by mixing ionomer (D) and olefin copolymer (]) with a mixing ratio of 3: 7. As a result, the shoulder position became of bubbles on the hot water bath and the orientation ratio at a transverse orientation ratio stabilized from 3.2 and a continuous orientation made no difficulties.

Example 4

The procedure used in Example 2 was followed by changing the following items from conditions described:

(a) The inner layer resin was replaced with a blend that was replaced by a blend of olefin copolymer (G) and ionomer (E) had been obtained at a mixing ratio of 4: 6;

(b) The skin resin was replaced with a blend obtained by blending olefin copolymer (H) and polyolefin (F) had been obtained at a mixing ratio of 5: 5;

(c) The thickness ratio of the outer layer to the core layer to the inner layer became 1: 1: 3 modified;

(d) the total thickness of the three layers was changed to 300µ;

(e) the temperature of the hot water bath was changed to 95 ^° C .;

(f) The core layer resin was replaced with vinylidene chloride copolymer (C).

The result showed that a transverse orientation of 3.2 with a longitudinal orientation ratio of 3.1 became possible.

The obtained film was remarkably improved in cold resistance and heat resistance compared to the film obtained in Example 2.

Example 5

The procedure used in Example 2 was followed by changing the following items to those described Conditions carried out:

(a) The skin resin was replaced with a blend that was made by blending olefin copolymer (H) and ionomer (D) had been obtained at a mixing ratio of 3: 7;

(b) the core layer resin was replaced with vinylidene chloride copolymer (B);

(c) the inner layer resin was replaced with olefin copolymer (H);

(d) The thickness ratio of the outer layer to the core layer to the inner layer became 2: 1: 4 modified;

(e) the total thickness of the three layers was changed to 686μ.

(f) the lengthwise orientation ratio was changed to 3.5

As a result, orientation with a transverse orientation ratio of 3.5 became possible.

Compared with the film obtained in Example 1, the obtained film was remarkably improved Resistance to cold.

Example 6

The procedure used in Example 2 was followed by changing the following items from conditions described:

(a) The skin resin was replaced with a blend that was made by blending olefin copolymer (J) and ionomer (D) at a mixing ratio of 1: 9.

II)

(b) the core layer resin was made by vinylidene chloride copolymer (C) replaced;

(c) the inner layer resin was replaced with olefin copolymer (I);

(d) The thickness ratio of the outer layer to the core layer to the inner layer became 1: 14: 5 modified;

(e) the total thickness of the three layers was changed to 500 µ and the flat width to 150 mm;

(f) the lengthwise orientation ratio was changed to 3.0.

As a result, orientation became with a cross-orientation ratio of 3.3 possible, but the resulting film was more suitable for use in lamination with the other base material than suitable for use as a single substance film.

Example 7

The procedure used in Example 2 was carried out with the following changes from those therein conditions described.

(a) The skin resin was replaced with a blend obtained by blending olefin copolymer (H) and ionomer (D) had been obtained in a mixing ratio of 4: 6;

(b) the core layer resin was made by vinylidene chloride copolymer (B) replaced;

(c) the inner layer resin was replaced with olefin copolymer (H);

(d) The thickness ratio of the outer layer to the core layer to the inner layer became 12: 1:14 amended;

(e) the total thickness of the three layers was changed to 800μ;

(f) the lengthwise orientation ratio was changed to 3.0.

As a result, orientation became with a lateral aspect ratio of 33 possible.

The resulting film had the most excellent non-leachability and cold resistance among them Slides in all examples.

Example 8

The procedure used in Example 2 was carried out with the following changes from those therein conditions described

(a) The skin resin was replaced with a blend obtained by blending olefin copolymer (K) and ionomer (D) had been obtained in a mixing ratio of 1:17;

(b) the core layer resin was made by vinylidene chloride copolymer (B) replaced;

(c) the inner layer resin was replaced with olefin copolymer (G);

(d) The thickness ratio of the outer layer to the core layer to the inner layer became 18: 1: 1 modified;

(e) the total thickness of the three layers was changed to 800μ;

(f) the lengthwise orientation ratio was changed to 4.0.

As a result, orientation became with a cross orientation ratio from 4.0 possible. The resulting film had the special characteristics that it one possessed high elastic modulus, rigidity and good transparency because it had a high content of ionomer.

JO

Example 9

The procedure used in Example 2 was carried out with the following changes from those therein conditions described.

(a) The skin resin was replaced with a blend made by blending olefin copolymer (I) and Ionoi:; · :! (D) was obtained in a mixing ratio of 4: 6.

(b) the inner layer resin was replaced with olefin copolymer (I);

(c) The thickness ratio of the outer layer to the core layer to the inner layer became 2: 1: 4 modified;

(d) the total thickness of the three layers was changed to 588μ;

(e) the diameter of the three-layer coextrusion die was changed to 65 mm;

(f) the flat width of the three-layer tubular product was changed to 85 mm;

(g) the lengthwise orientation ratio was changed to 3.4;

(h) The temperature of the hot water bath was changed to 85 ° C

As a result, orientation with a transverse aspect ratio became of 3.53 possible, but the internal pressure of the bubbles was during the orientation somewhat high compared to the case of Example 4.

The data for the stretched films from Example 1 to Example 9 are summarized in the table.

Tabel

example / Art
\ Thickness
/ Art
1 thickness
[Art
(Thickness unit example 1 Example 3 Example 4 Example 5 Outer layer
Core layer
Inner layer Orientation
ratio of the slide
(MD / TD) *) μ
μ
μ A.
15th
50% D, 50% J
35 30% D, 70% J
12th
A.
36
J
12th 50% H, 50% F
10
C.
10
40% G, 60% E.
30th 30% H, 70% D.
16
B.
8th
H
32 factor 3.0 / 3.0 3.1 / 3.2 3.1 / 3.2 33 / 3.5

lortset / uim

example

13th

unit

example 1 Example 3

Heat shrinkage% 21/25

at 80 ° C (MD / TD) ·) oxygen penetration cmVm ² -24hatm

21/30

Example 4

Cold resistance **)

Fall cycles to break

16/21

14.5 164

5 or less 5 or less! 5—30

Example 5

23/31

49.5

50 or more

Table (continued)

example

unit

Outer layer core layer

Art

Thickness μ ί Type 1 Thickness μ

I At- *

Inner Slides 1

Example 6 Example 7

BeisDiel 8

Example 9

Thickness μ

Orientation factor

ratio of the film (MD / TD) *)

Heat shrinkage% 18/28

at 80 ⁰ C (MD / TD) *) oxygen permeation CMVM ² · 25 h · atm 46.7

10%], 90% D.

35

40% H, 60% D.

36

B.
3
H
42

3.0 / 3.3

28/30

152

5.5% K, 94.5% D 40% I, 60% D

45 14

B A

2.5 7

G I

2.5 28

4.0 / 4.0

21/33

183

3.4 / 3.53

22/31

75 30-50

Cold resistance **) Drop cycles up to 5 or less 50 or more 15-30

Remarks:
*) MD / TD is an abbreviation for machine direction / transverse direction (equal to transverse direction).

**) Procedure for measuring cold resistance:

A bag with a width of 500 mm and a length of 800 mm was made using a film Bag was placed in beef weighing approximately 4.5 kg, which was cooled to -2.5 ° C to 2.5 ° C. The that Bags containing raw beef were horizontally placed on a polyvinyl chloride plate 20 mm thick from a Dropped 1.5 m high in a room with a room temperature of 2 to 3 ° C. The fall cycles were measured by the bag was dropped until the film broke or tore such. B. began to have a pinhole.

Claims (3)

Patent claims: 1. Biaxially stretched tubular multilayer film with gas barrier properties, thereby characterized in that they have a gas barrier layer made of vinylidene chloride copolymer, which consists of 65 to 95% by weight of vinylidene chloride and 35 to 5% by weight of one or more unsaturated monomers copolymerizable with the vinylidene chloride and one or more cold-resistant, J. h. Retaining their properties under cold Layers of polyolefin or a mixture of polyolefin (homopolymer) and olefin copolymer, which adhere firmly to the gas barrier layer attached, said layers having been fused together; that at least one of the cold-resistant layers contains an ionomer; that the thickness of the gas barrier layer is 3 to 70% based on the total thickness of these layers, and the thickness of one or more of the cold-resistant layers at least 5%, based on the total thickness of these Layers, and that is the entire volume of the in one or more of the cold-resistant layers contained ionomer is 4 to 85%, based on the total volume of these layers 2. A biaxially stretched tubular multilayer film according to claim 1, characterized in that the olefin copolymer or the mixture, when the crystal melting point of the same using a differential Abtastcalorimeters is measured, having the peak of the crystalline melting point ranging from 60 ° C to 110 ⁰ C. 3. Biaxially stretched tubular multilayer film according to claim 1, characterized in that that the film is a tubular multilayer film having an orientation ratio of 2.5 to 5 each is oriented in the longitudinal direction and transverse direction.