DE2644209A1 - COMPOSITE FILM - Google Patents

Description

TORAY INDUSTRIES, Inc.

2, Nihonbashi-Muromachi 2-chome

Chuo-ku, Tokyo, 103 Japan

Composite oil ie

The present invention relates to a composite film which except for good water resistance and good mechanical Properties also have excellent gas impermeability having.

Saponified ethylene / vinyl acetate copolymers (hereinafter referred to as "polymer A") are used for production used by films with gas barrier properties, both undrawn and in one Direction of little, i.e. less than 1.8 of the original length, stretched films. As these slides only very are not very water-resistant, they are usually made using a suitable adhesive with polyolefin and / or Laminated polyester foils. Have the laminated foils however, several disadvantages. When the laminated film is used for packaging water-containing goods

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or at high temperatures and high humidity stored, small wrinkles and puckers form on the surface of the composite film in a short time Absorption of water by the polymer A occurs, and the film eventually dissolves into its individual Layers on what is also known as delamination.

Since the layer of the polymer A must be more than 15μπι thick in most cases in order to be as small as possible To ensure gas impermeability, the laminated film is also quite thick and can therefore be used for many uses do not handle well.

In the case of lamination using adhesives, manufacturing difficulties sometimes arise, since folds, air inclusions, solvent residues and the like can only be avoided with difficulty and the adhesive strength is not always uniform. In addition, the production costs of the laminated film become very high because the yield is lower.

In view of these disadvantages, the object of the present invention was to create an improved composite film,

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which has excellent gas impermeability.

The above-mentioned object is achieved by a composite film with a base film made of polypropylene, whose distinguishing feature is that they have an intermediate layer of a polymer B from a modified Polyolefin and an outer layer made from a polymer A made from a saponified copolymer Ethylene and vinyl acetate, which contains 20 to 50 mole percent ethylene units and which is saponified to an extent of at least 90% is, has, wherein the layers of the polymers A and B are oriented essentially in only one direction, while the polypropylene base film is biaxially oriented. The thickness of the individual layers in composite A: B: C preferably corresponds to 1: 0.05-10: 5-40.

In addition to its excellent gas impermeability, the composite film according to the present invention has others Benefits on.

The composite film with the layer of the polymer A on its surface has excellent gas barrier properties and good water resistance and maintains its smooth appearance even in a high environment Temperatures and high humidity.

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Due to the structure of several layers, their mechanical strength values, i.e. impact strength, Tear strength and the like, significantly improved.

The stretchability of a web made of the composite film that consists of layers A and B applied by extrusion and a longitudinally stretched layer C, in one The stretching frame is significantly improved compared to a film that consists only of polymer A.

If the surface of the film consisting of the polymer A can be extruded or glued with a heat seal capable layer, such as a layer made of polyethylene or an ethylene-propylene copolymer, In addition to heat-sealing properties, the corresponding composite film also has better water resistance and therefore remains lighter when exposed to water smooth and does not dissolve into its layers even at high temperatures and high humidity.

A composite film, which consists of a corona treated, biaxially oriented polypropylene film, onto which a layer is first extruded

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• J.

from a saponified copolymer of ethylene and Vinyl acetate and then a layer of polyethylene had been applied, has the same structure as the composite film according to the present invention, but has insufficient gas barrier properties and water resistance, because the layer of the saponified ethylene / vinyl acetate copolymer is not oriented and the individual Layers are not sticking together tightly. Therefore, the flatness of the film surface deteriorates, if they are stored at high temperature and high humidity or if they are water-containing for packaging Materials used.

The polymer A according to the present invention has a content of 20 to 50 mol percent, preferably between and 40 mol percent, of ethylene units and a degree of saponification of more than 90%, preferably above 95%; a film of this composition can be melted State and retains its excellent gas impermeability. The limiting viscosity number of the Polymers A, measured in a solvent mixture from 85 percent by weight phenol and 15 percent by weight water is between 0.07 and 0.17 l / g, preferably between 0.09 and 0.15 l / g.

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When the intrinsic viscosity of the saponified polymer falls below 0.07 l / g, the layer made of this polymer within the film composite is brittle and forms easily cracks during stretching through which the Gas impermeability and water resistance of the composite film be affected. When the limiting viscosity number is more is than 0.17 l / g, the extrusion temperature approaches the decomposition temperature of the polymer. This creates Air inclusions in the layer or at the interfaces between the layers, which increase the risk of the film delaminating or delaminating during stretching rips off.

Depending on the use for which the composite film according to the invention is intended, the polymer A can also Additives such as stabilizers, antioxidants, plasticizers, fillers, crystallizing agents, lubricants, antistatic agents and the like can be added. A mixture with other polymers is also possible, as long as this does not change the properties of polymer A too much.

The modified polyolefin also described in the present invention (hereinafter referred to as "Polymer B"

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2644203 ' AA .

contains functional polar groups. According to the According to the invention, the following compounds can be used as polymer B:

1. Polyolefins, for example polypropylene, polyethylene and the like. Which are graft polymerized with at least one monomer from the group of X , 13-ethylenically unsaturated dicarboxylic acids, such as maleic acid, fumaric acid, itaconic acid or their anhydrides, acid esters, acid amides and acid imides.

2. Copolymers of ethylene with acrylic acid, methacrylic acid, J. , ß-unsaturated carboxylic acids, and / or their metal 1 salts.

3. Graft-polymerized polyolefins salt with J ,, ß-unsaturated carboxylic acids and / or their alkyl esters or acid metals.

4. Saponified copolymers with a monomer of Above-mentioned unsaturated acids are graft-polymerized.

The polymers mentioned under 1. and 2. are preferred

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wisely used for the present invention.

Examples of suitable polymers B are in particular less than 1.0 percent by weight mitoi, ß-äthyleni sch unsaturated dicarboxylic acids (preferably maleic anhydride) graft polymerized polyolefins, e.g. Polypropylene, copolymers of ethylene and propylene, polyethylene and the like.

The biaxially stretched polypropylene layer consists of a polypropylene (hereinafter referred to as "polymer C") which is either a homopolymer of propylene or a copolymer of propylene and ethylene, butene, hexene and / or other oU-olefins.

The limiting viscosity number of the polymer C, measured in tetralin at a temperature of 135 ° C, is between 1.6 and 2.7 dl / g, preferably between 1.8 and 2.3 dl / g, and the isotactic index is between 85 and 99%, preferably between 90 and 98%.

An admixture of other polymers such as polyethylene, poly-4-methyl-pentene-1, polyterpene, naphtha derived hydrogenated petroleum resins, copolymers of ethylene and vinyl acetate, polymers] B and the like. is possible as long as the properties of the

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Polymers C are not changed too much.

Depending on the intended use, additives such as antioxidants, antistatic agents, fine dispersed inorganic substances, pigments, plasticizers, organic lubricants and the like can be added.

The thickness of the layer made from polymer A is determined by the desired gas impermeability of the finished product Composite film and is in most cases less than 15μπι, preferably between 1 and 10μπι, since the composite film according to the invention, compared to the conventional laminates, excellent gas barrier properties owns.

When the thickness of the polymer C layer is less than five times the thickness of the polymer A layer is, the mechanical properties and dimensional stability of the film deteriorate high temperatures. When the thickness of the layer of the polymer C is more than 40 times the thickness of the layer from the polymer A, the heat seal strength of a packaging material in which on the layer of the polymer A a heat sealable

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Layer is applied. Because this increases the speed e.g. during the bag manufacture is impaired, productivity decreases.

If the thickness of the polymer B layer is less than 5% of the thickness of the polymer A layer, the adhesive strength of the two layers is insufficient and the composite film tends to delaminate when stored at high temperature and high humidity.

If the thickness of the layer made of the polymer B exceeds the thickness of the layer made of the polymer A, that is Adhesive strength of the layers is sufficient, but because the layer made of the polymer B is too thick, it suffers Transparency of the composite film, e.g. when reusing film waste or seam strips, which is normally the case is common in film production.

The composite film according to the invention can according to the im

can be produced in the following described processes. It

however, there should be no restriction to this method.

Polymer A and Polymer B are in different

Extruders melted and combined on one in one Directional film extruded from polymer C,

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either through an adapter, which is arranged in the supply line in front of a simple distributor nozzle or through a double distributor nozzle. The thickness of the layer composed of the polymer A to the thickness of the layer composed of the polymer B corresponds approximately to the ratio A: B = 1: 1-0.05.

On the other hand, the polymer C can also be melted in another extruder and cooled on a casting drum in order to produce an unstretched film, which is then reduced to 3 to 10 ° ^{C. at temperatures between 90 and 150 °} C., preferably between 110 and 140 ^{° C.} -fold, preferably 4 to 7 times _{9 of} their original length is stretched in the longitudinal direction. Layers of polymer A and of polymer B are then applied by extrusion to the film made of polymer C and stretched in one direction, so that the sequence ABC results.

When lamination should be applied to the layer from the Layers of polymers A and B applied to polymers C are preferably less wide than the width between opposing clips of the stretching frame, so as to increase the proportion of polymer A and polymer B

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in the lined edges of the film.

In order to achieve good stretchability, the polymer A can contain water during the extrusion, preferably an amount of 1 to 10 percent by weight, or the laminated film can be washed again with hot water or hot steam.

Subsequently, the laminated film to temperatures between 120 and 180 ⁰ C, preferably heated from 140 to 165 ⁰ C _5, 15-fold to 5 to, preferably 12-fold-to 7- to, stretched transversely of its original width, and then heat-set at a temperature between 130 ⁰ C, preferably between 140 ⁰ C, and a temperature 5 ° C below the melting point of the polymer a. The gas impermeability, water resistance and other properties of the composite film are significantly improved by the stretching and heat setting, and the improvement is even more considerable if the polymer A contains water during the stretching.

When the temperature used for heat setting higher than 5 ° C below the melting point of polymer A, not only will the good physical

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Properties of the composite film, its mechanical properties, its gas impermeability, its water resistance, etc., impaired, but the composite film also tends to tear off during heat setting. If the temperature used for the heat setting is lower than 130 ^° C., the heat setting has no noticeable effect.

Likewise, the layers of polymer A and polymer B can also be stretched in the transverse direction Film extruded from the polymer C and the composite film thus produced is then stretched in the longitudinal direction will.

The statement that the layers made from polymers A and B are "essentially oriented in only one direction" has the following meaning:

Layers made from polymers A and B normally experience molecular orientation through a stretching process. However, if the stretching temperature of the laminated film is higher than the melting point of polymer B, the layer of polymer B melts and begins to flow, losing its molecular orientation.

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When the temperature used for heat setting is higher than the relaxation temperature of the polymers A and B, the molecular orientation of the polymer A tends and B to disappear. For these reasons, the present invention has these specific conditions prescribed for stretching and / or heat setting.

The properties of the composite film according to the present Invention are determined by the following methods:

1. Oxygen permeability (cm / m χ 24h - material in

Leaf shape).

The oxygen patency apparatus "Oxy-Tran 100" from Modem Controls Inc., USA, was used. The measurements were carried out at a temperature of 20 ^° C. and a relative humidity of 100%, and a film sample was used which had previously been ^{stored for one day at a temperature of 20 °} C. and a relative humidity of 100%.

2. Water resistance

The composite film is immersed in water at 90 ^° C. for 30 minutes

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cooked. The appearance of the composite film is then tested and assessed according to the following criteria: ^{Good :} The flatness of the surface of the

The composite film before and after the boiling test is unchanged.
Δ Poor: The flatness of the film surface

changes easily.

X Bad: The flatness of the film surface is

changed significantly.

β . Shrinkage behavior under the influence of heat

A composite film is placed for 15 minutes in an oven, the temperature of which has been set to 120 ^° C., and the changes in the dimensions of the film are then determined.

4. Heat seal strength

The layer consisting of the polymer A of the

Composite film is so with a polyurethane adhesive

coated so that the layer formed 0.5 g / m 2

weighs. A 40μπι thick film is then made a low-density polyethylene laminated onto the film coated with the anchoring agent. The heat seal strength is determined by

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■ ic

the film laminated by gluing through

Heat sealing (with yourself) connects what to do with

2
a pressure of 1 kg / cm for 0.5 sec. a temperature

from 140 ⁰ C can act.

example 1

Polymer A: A saponified copolymer is used with 33 mole percent ethylene units, a degree of saponification

of 99 mol percent, an intrinsic viscosity of 0.12 l / g and a melting point of 178 ° C.

Polymer B: A polypropylene with an intrinsic viscosity of 2.2 dl / g and an isotactic one is used 97% index that was 0.4 weight percent graft polymerized with maleic anhydride.

Polymer C: A polypropylene with an intrinsic viscosity of 2.2 dl / g and an isotactic one is used Index of 97%.

The polymer C was extruded at a temperature of 285 ° C. and cast films of 800 μm and 1,200 μm (for slide no. 2) thick. With the help of stretching rollers, the cast film was stretched in the longitudinal direction onto the

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264-209

five times its original length. The polymers A and B were melted in separate extruders, extruded them together at 240 ^° C. through an adapter arranged in the feed to a simple distributor nozzle, and laminated them in the order A / B / C to the carrier film stretched in one direction the polymer C.

The thickness ratio between layers A and B could be can be set via the speed of rotation of the extruder screw.

The surface of the layer composed of the polymer A was ^{exposed to water vapor at 105 °} C. and the water content of the layer A was adjusted to 8 percent by weight.

The laminated film was then stretched in the transverse direction to 8 times its original width using a stretching frame and finally fixed ^{in the transverse direction at 160 ° C. with a relaxation of 5%.} The gas barrier properties and physical properties of the composite film produced in this way are listed in Tab. 1.

The composite films according to the present invention (films

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1 to 4) are characterized by good gas impermeability. As for the evenness of the surface after the boil test As for the films, the films were free from defects, had good water resistance, and were also at elevated temperatures dimensionally stable. The film no. 5 had insufficient water resistance, because the polymer B layer was too thin.

The heat seal strength of the composite films according to Invention (Foil No. 1 to 4) was between 1.0 and 1.2 kg / cm. However, the film No. 5 was insufficient Heat seal strength (130 g / cm) and was unsuitable for practical use because the composite film delaminated.

In the case of film No. 6, the layers shrank under the influence of heat and the film tended to be closed pucker because the polymer C layer was too thin. Since film no. 6 is used in! .Lamination and in which made heat sealing more difficult to process, it is for the use as packaging material is not particularly suitable.

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TABEL

O CO 00

CD

O 00 co Ut

No. of
foil thickness Thickness of the composite film
the layer thickness ratio C. A. 0 B. C. Oxygen-
permeable water
strength Shrink at
Heating across A. (pm)
B. 20th 1 0 1 10 cm ³ / m ² χ 24h along 0.4 1 2 2 30th 1 0 1 15th 6.6 O 3.3 0.3 2 2 2. 20th 1 0 , 25 5 6.5 O 3.4 0.7 3 4th 1 20th 1 , 075 5 3.2 O 3.0 0.8 4th 4th 0.3 20th 1 , 04 5 3.3 C. 3.0 0.8 5 4th 0.16 10 1 , 25 2.5 3.3 A ^ X 3.1 2.5 6th 4th 1 3.3 O 3.1

t / 4

CD -F-

NJ CD CjO

Example 2

Polymer A: A saponified copolymer with 28 mol percent ethylene units was used, one Degree of saponification of 99 mol percent, an intrinsic viscosity of 0.15 l / g, and a melting point of 179 ° C.

Polymer B: A polyethylene was used with a

Melt index of 0.8 g / 10 min., And a density of

0.93 g / cm, that with maleic anhydride (0.5 weight percent) had been graft polymerized.

Polymer C: A polypropylene copolymer was used with 0.7 percent by weight of ethylene units, one Limiting viscosity number of 2.0 dl / g and an isotactic one Index of 96 percent by weight.

One extruded the polymer C at 280 ⁰ C to a cooled to 30 ⁰ C casting drum, and provided a cast film of 800μιη thickness (for the films Nos. 7 to 12) and a cast film of 1 800μιη thickness (for the film no. 13) here. The film was then at 120 ⁰ C to five times its original

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union length stretched in the longitudinal direction. The polymer A, which had a water content of 3 weight percent and the polymer B were co-extruded at 200 ⁰ C and laminated in the order of A / B / C on the stretched film in a direction from the polymer C.

The composite film thus produced was subsequently made five times its original in the transverse direction Stretched wide and fixed at different temperatures, for which one used a stretching frame and one Relaxation of 1% in the transverse direction allowed. The properties of the composite film are shown in Table 2 below to see.

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No. of thickness Thickness of the composite film C. ie TABEL : B. : C 2 temperature Oxygen- water foil of the layers 20th : 1 : 20 in the permeable strength 20th Thickness ratio : 1 : 20 Thermal 20th : 1 : 20 fixation A. (μιη) ( ⁰ C) cm ³ / m ² χ 24h 1 B. 7th 1 1 A. 160 13.0 O 8th 1 1 20th 1 : 0.25 : 5 140 13.3 C. -4 9 1 20th 1 : 1 : 20 130 13.7 O O
CO 20th 1 : 1 : 20 OO Ver Il equal 4th 20th : 4 : 20 no co, example 1 1 45 : 1 : 45 Fixation 105.0 X 10 1 1 1 100 32 Δ ~ X CO ' 11 1 1 no 35 X cn 1 1 Fixation 12th 1 ' 4th 140 13.2 O 13th 1 1 140 13.0 O 1

The composite films according to the present invention (films Nos. 7 to 9), which were set at temperatures above 130 ⁰ C, showed good gas barrier property and water resistance.

Films Nos. 10 and 11 were poor in gas impermeability and water resistance because none Heat setting has been carried out or the ones applied Temperatures were not high enough to have these properties to improve.

Film no. 12 had a thick layer of polymer B and was therefore unsuitable for re-using the trimmed Edges or film waste. With a corresponding The test showed film no. 12 in which the layer composed of polymer C had 50 percent by weight of film waste added to No. 12 film had poor transparency and 15% haze, while a film No. 12 made without the addition of foil waste had good transparency and only 2.8% haze.

On the other hand, a No. 7 film mixed with scrap film in the same manner was the

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Transparency was good and the haze was only 3.0%. In the case of film No. 13, the heat seal strength was poor (150 g / cm) because the polymer C layer was too thick. To produce a good seal strength, they were closed long heat sealing times required.

Comparative example

A 20 μm thick, biaxially stretched film made from the polymer C according to Example 1 was treated with a corona discharge. Subsequently, layers of polymers A and B were extruded onto the treated side of the film made of polymer C, so that a composite film of type A / B / C (4/1/20 μm) similar to the film was produced. It was very difficult to extrude layers A / B onto layer C evenly. The oxygen permeability of this composite film was 105 cm ³ / m ² 24h (material in sheet form). Splitting of the film between layers B and C was observed in a boiling test.

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Claims (16)

PATENT CLAIMS Composite film with a base film made of polypropylene, characterized in that it has an intermediate layer made from a polymer (B) made from a modified polyolefin and an outer layer composed of a polymer (A) composed of a saponified copolymer composed of ethylene and Vinyl acetate, which contains 20 to 50 mole percent ethylene units and is at least 90% saponified, having, the layers of the polymers (A) and (B) oriented essentially in only one direction are, while the polypropylene base film (C) is biaxial is oriented. 2. Composite film according to claim 1, characterized in that that the thickness ratio of layers A: B: C 1: 0.05-10: 5-40. 3. Composite film according to one of claims 1 or 2, characterized in that the polymer layer (A) carries a heat seal layer (D). 4. Composite film according to one of claims 1 to 3, characterized in that the polymer layer (A) consists of one - 25 - 709819/0895 original inspected Copolymer is built up with 25 to 40 mol percent ethylene units. 5. Composite film according to one of claims 1 to 4, characterized in that the polymer (A) consists of a copolymer exists that is at least 95% saponified. 6. Composite film according to one of claims 1 to 5, characterized in that the polymer (A) has a limiting viscosity number from 0.07 to 0.17 l / g. 7. composite film according to one of claims 1 to 6, - characterized characterized in that the layer of the polymer (A) additives such as stabilizers, antioxidants, Plasticizers, pigments, crystallization agents, Contains antistatic agents and lubricants. 8. Composite film according to one of claims 1 to 7, characterized in that the polymer (A) consists of a copolymer that contains additional polymers. 9. Composite film according to one of claims 1 to 8, characterized in that the polymer (B) consists of a - 26 709819/0895 26U2Q9 • 3 Polyolefin that contains functional polar groups. 10. The composite film according to any one of claims 1 to 9, characterized in that the polymer (B) consists of a polyolefin which with at least one monomer from the group of JL. , ß-äthyleni cal unsaturated dicarboxylic acids is graft polymerized, or from copolymers of ethylene with acrylic acid, methacrylic acid, /, ß-unsaturated carboxylic acids and / or their metal 1 salts, consists. 11. composite film according to one of claims 1 to 10, characterized in that the polymer (C) of the base layer consists of a copolymer of propylene and ethylene, butene, hexene and / or others ^ -Olefins, consists. 12. Composite film according to one of claims 1 to 11, characterized in that the polymer (C) of Base layer has an intrinsic viscosity of 1.8 to 2.3 dl / g. 13. Composite film according to one of claims 1 to 12, - 27 - 7098 19/0895 characterized in that the base layer made of the polymer (C) contains additives such as antioxidants, Contains antistatic agents, pigments, plasticizers and lubricants. 14. A method for producing a composite film according to any one of claims 1 to 13, characterized in that that the polymers (A) and (B) are coextruded and on a prefabricated film stretched on one side Polymers (C) extruded on. 15. The method according to claim 14, characterized in that one in the orthogonal direction to the already stretched direction carried out. 16. The method according to any one of claims 14 or 15, characterized in that the polymers (A) and (B) applying a longitudinally stretched film made of the polymer (C). - 28 - 7098 1 9/0895