DE1694694A1 - Heat sealable laminate - Google Patents

Description

The invention relates to a laminate based on a oriented polypropylene film which is improved in terms of its heat sealability and other properties.

In recent times, thermoplastic films are on the rise Extensive application in the field of flexible VerpaokungsfοIien. Self-supporting thermoplastic »* films, such as polypropylene films, have a high resistance to the passage of water vapor. This property is of particular advantage for the packaging of moist foods, because the moisture content of the food is retained over long periods of time. Another advantageous property of polypropylene is its durability, so that the food leased in the foil easily

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are verifiable. Furthermore, polypropylene film is tough at deep. Flexible at temperatures, dimensionally stable up to temperatures close to the softening point and against most solvents and chemicals resistant. Polypropylene is non-toxic, odorless and tasteless.

Polypropylene film is because of its low weight per unit area and their low cost is of particular interest for use as a flexible packaging film.

It is known that various physical properties of thermoplastic films, such as clarity, gloss, tensile strength and brittleness at low temperatures, are important Let orientation improve. This is particularly true of polypropylene. Oriented polypropylene is characterized by its properties, such as modulus of elasticity »tensile strength, elongation at break, Impact resistance and shrinkage energy significantly superior to unoriented polypropylene. Orientation is achieved by heating and stretching the film in the longitudinal or machine direction (the direction in which the film passes through the production line) and in the transverse direction (the viewing perpendicular to the direction in which the film is running) or in both views brought about. During this orientation process, the polymer molecules are oriented from their original random distribution in the orientation direction, whereby

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a significant improvement in packaging nasal properties of the film is achieved.

Although the ability of polypropylene to undergo exposure of heat and pressure to adhere to itself, i.e. those for The heat sealability required for processing the film into packs is just satisfactory before orientation, but is by no means after orientation sufficient. As with most other types of oriented thermoplastics, oriented also performs Polypropylene is used for reheating to the softening point of the film, as must be done with hot bars Return of the polypropylene molecules to their original random distribution, causing the film to shrivel, wrinkled becomes and travels. This property of oriented polypropylene films creates difficulties when trying to heat seal the foils in the usual way.

To overcome these difficulties, it has been proposed to coat the oriented film with various heat-sealable substances, such as polyvinylidene chloride or polyvinyl acetate, nitrocellulose and many other * substances or combinations of substances. S , lohe coatings are usually made from solvents awfgebr? e? it, «* e costly, especially for this .ik be; «Iramte * echi" ^ ings- and solvent recovery

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plants required. In order to ensure that these coatings adhere to the polypropylene carrier, it has been found necessary to subject the film to a special treatment * There are various treatment methods for this, e.g. treating the film with a corona discharge or chemical treatment of the film with ozone, SuIfοChlorierung, the oxidation with liquids or with the flame or the application of a primer coating in order to bind the thermoplastic top coating to the polypropylene carrier foil. Flame treatment processes are described in patents in order to make polypropylene film heat-sealable. Treatments with solutions, glow light discharge and coating processes to improve the Eeiaaiegelbarkeit of polypropylene films are also known from patents.

It is also known that the heat sealability of oriented Polypropylene film by encasing heat-sealable improve thermoplastic films au. So it has been suggested on PoI ^. vpylenfolien for this purpose polyethylene, MisohpolymerliWte «ies Xthylens, Polyallomere, Polystyrene, To accumulate polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, copolymers of ethylene and vinyl acetate or nitrocellulose. The invention relates to a new laminate based on oriented polypropylene film, which has significantly improved heat sealability has kelt.

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The laminate based on oriented polypropylene film according to the invention, which is improved in terms of its heat-sealability, consists of a carrier film made of oriented polypropylene to which at least one heat-sealable thermoplastic layer made of a copolymer of ethylene and propylene is firmly bonded, which consists of a »monomer mixture of about 2 to 6 wt .- $> ethylene and 98 to 94 wt .- # propylene is produced. If the heat-sealable high-polymer layers are laminated onto both sides of the polypropylene carrier film, a laminate is obtained; with a polypropylene core and outer holes made from the copolymer of ethylene and propylene, which is uniformly heat-sealable. According to another embodiment of the invention, a laminate consisting of three soles can be slit in the longitudinal direction, whereupon the individual parts are placed on top of one another and joined together to form a laminate composed of two laminates.

The laminate obtained in this way has heat seal strengths In the Masohinenriohtung and in the transverse direction of more than 100 g / 25.4 na over a temperature range of 15.56 ° C. Furthermore, the laminate shows an extraordinary resistance to aging, in that samples of it even after 50 days of Ie

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heat seal range of 4.44 ° C. This is in contrast to simple, oriented polypropylene films as well as polypropylene foils with laminated thermoplastic films made of polyethylene or a polyallomer. significantly lower resistance to aging.

The laminate made of polypropylene and the copolymer of ethylene and propylene according to the invention also has in Another relationship advantageous mechanical properties Compared to the commercially available, coated, oriented polypropylene films, the one according to the invention suffers Laminate has no pitting, no dulling, no icing, it has no lack of gliding ability shows no coating streaks or sensitivity to moisture; also possessed the laminate according to the invention also better optical clarity. The product of the invention made up of two laminates has a particularly high tensile and impact strength at low temperatures compared to simple, oriented polypropylene films.

Me erfindungegeBäeeen thickness of the laminates based on oriented "polypropylene depends on the intended use beaboichtigten * for packaging svecke the thickness of the laminate is μ in the range of about 2.5 to 0.5 anu, upstream

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suggests from about 5 to 25 μ. The desired film thickness is achieved by suitable selection of the working parameters during extrusion or during the other deformation process for the production of the layered toffee as well as the heek ratio used for orientation,

The laminate has adhesive layers on the two opposite sides of the oriented polypropylene film. TxuB the heissiegelbareii copolymer aas ethylene and propylene to "HisciipolyEiörisat This is prepared from a Monoioerer.-gemiseh that atvra bia 2 wt .- ^ 6, preferably about 2.3 to 3» 8 wt. ™ _4>} contains ethylene and Reet is made of propylene. The Mcfcs of each of the "bsiaen heat-sealable" outside ohts kmm. etv / a 5 to 15 # »Tcraugeweiae about 10 pounds per the grain thickness of the laminate. For Verpaokungsswecke the mosquito is the heat sealable. Layers preferably in the range τοη. -Jt about 0.76 to 2.5 μ.- Although the thin outer layers E a \, f Sars oriented Srölypropylene core only a little steep up to the weight of the carbon, e.g. not more than about 10 $ _t bai ^ ut-. 'agen hz-av.cl ^ r ^ it & lX-.n they gle3. ^ ". ^. 3sige, slightly äeiefliogöl'jfti:. ·' · Jl ^ flädhun for the oriented® $ c \ y? * r > pr '* % nfcl <and adhere to polypropylene without the use of a binding agent.

ORiQiHAL INSPECTED

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The laminate based on orienties-tcs? Polypropylene film according to the invention of kana n & oh. any process for the production of oriented foils can be used · It is however important to have a biaxial orientation, ie. eino orientation both In dsr Maechinenrißhtußg as t.i2oh in dos? Transverse direction; of each layer of both the carrier film made of polypropylene as well as the healable KioohpolyciEriBat-'Außsoß.BisJiiofetf.irA, h.-Ef;? ii; leadcm. The laminate can uroprünglioh iinfciittfriliar ev? » άοη in the fair available four-faced fabrics for aii th produced v; earth ₅ eB ₀ with the B after the B ^ eii'band injection process or according to the previous arises. This common extrusion k & Xvci with "bskannts species with known devices By J ^ igeführi: word on.

The biaxial orientation of the laminates can also be carried out in a known manner. For example, the orientation kexca Wfcn in successive work steps in front of the door, in that the film sealant in separate process steps "first in the longitudinal or machine direction and then in the transverse direction and, if a balanced film is required,

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aneekXieosend is stretched again in the longitudinal direction.

The biaxial orientation of the laminate can also be carried out by making the pollen layers at the same time stretched both in the longitudinal direction and in the machine direction. A further modification can be the biaxial Orientation of the laminate is made by aan the layer st off in sequence first in the machine direction j then stretched in the transverse direction and these operations repeated one or more times, each one Stretching process on its own, for complete orientation not enough.

The longitudinal stretching of the laminate can be carried out in any known manner, e.g. between a series of rollers running with Rotate at different speeds · Also known devices for the transverse stretching of continuous Sheets or films can be used to give the laminate the desired transverse orientation. Used preferably However, the tenter frame that is common in the textile industry is used to carry out the transverse stretching.

The tensile and impact strength of the biaxially oriented polypropylene sole material according to the invention can be improved

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are indened to produce a double-layer material, i.e. by slitting open the film web and stacking the individual web sections on top of each other and cascading them on top of each other. on this way, nan-oriented polypropylene laminate is obtained, where two or more polypropylene carrier films by heat-sealable layers from the copolymer Ethylene and propylene are separated from each other and the two outer layers consist of the Miechpolyaerieat, so that the entire laminate has the improved heat sealability of the invention.

example 1

A laminate made of polypropylene and a mixed polymer of ethylene and propylene is produced by extrusion made inden a melted laminate web nit a speed of 76 to 82 n / kin · in a water bath is extruded. The laminate is in a bead of 17t β μ extruded; the proportion of the polypropylene carrier film

at this bead is 85 t, and the proportion of each of the two miso-polynerisatsohlohten on the outside of the carrier film is 7.5 * the Ge β to t thickness of the layered taffy.

The laminate is sucked off into the water bath, and that Excess water is blown off. Then the shift

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fabric torerliitzed and stretched in the machine direction by passing it between the legs of orphans heated to 104 Mb 121 ° C. One pair of whales runs at a speed of 82 m / min., The other at a speed of 122 m / min. In this way the film is stretched out by 50 ° ^C in the machine direction. The laminate pre-assembled in Mngsrichiurg is then fed to a Sptamrahiaen located in an oven. Ura the policy tone 5 <? E, occurs in the furnace Liifi / from 14-9 ° 0 on the f. The laminate vd.rd is stretched in the horizontal direction to eight times its original width. The mechanical properties and the hot seal bar kit of the finished laminate result from Tables I and XI '.

At spie 1 2

Following the procedure of Example 1, an oriented polypropylene sheet is made old with a thickness of 21.5 μ. The aechanj see Eigenocheften and the hot weldability this laminate can also be found in Tables I and II.

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Example 3 - double laminate

The procedure of Example 1 is followed by extrusion made a laminate with a thickness of 11.4 μ. After extrusion and quenching, the laminate is slit in the longitudinal direction into two sections of the same width, which are then laminated onto one another. This double-layer material is then biaxially oriented according to Example 1.

The mechanical properties and the heat sealability of the The double layer and the laminates produced according to Examples 1 and 2 are shown in the tables below.

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KDCO 122 T a b e 1 1 e example - 150 I. Example 3 • 1220 Mechanical properties 0.8 1.6 characteristic 2.0 ! Exercise after 0 sayings of laminates 15 days 91.0 1 at θυ! El 2 85.5 21 days 1.5 83.0 Shine after 0 days - 15 days 1.8 21 days 1350 83.9 1390 Push pull capability in
Machine direction after 450 • -β 1120 0 days 84.3 14 days 21 days 1050 36 days - Impact strength in
Transverse direction 400 15 to 21 days 1440

"Handle" machine direction: transverse direction

15 to 21 days 5 y 12.5 8 y

CoOoFo after

12 to 15 days 0.46 0.48 0.46

Tensile strength property en (after 8-21 days)

Yield strength in masonry direction, kg / om ² 429 394 387

Tensile strength in mastic direction, kg / ea ² 562 562

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Table I (continued) Property Example 1 Example 2 Example 3

Tensile strength properties (after 8-21 days)

Tensile strength in transverse direction, kg / cm ^ 4150 > 415O> 3800

Modulus of elasticity in machine direction, / ^

17 300 550 440 40 700 50 <40 495 36

Modulus of elasticity in the transverse direction, kg / cm

Elongation at break in masonry direction, Ί »

Elongation at break in the transverse direction, i>

The heat seal strengths given in Table II are measured on the basis of the heat seals of the films in question at the temperatures given in the table with sealing bar dwell times of 3.5 seconds and heat seal pressures of 30 g / 6.452 on ² . The letter "P" in the table means that a welded joint with a strength of 100 g / 25.4 m or more has formed, but it has not been measured. The letter ^N W * means that a welded connection is formed with such a strength that the film zerreiset even before the welding bond breaks.

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Tabel

II

Heiattleffel areas de? Layer fabrics

At 'Ölel 115.5 ⁰ O 126.7 ° C. 137.8 ⁰ C U8.9 ° C 160 ⁰ C 171.1 ⁰ C »„ «WM» W »Μ
_Λ ^ * αη 0 i'agett
in Maeohinenriohtung O 100 g W. ¥ W * nf ».ch 0 days
.α transverse direction O 100 g P. W. W. W. »Afc
O
((P after b days
la machine direction
and cross direction 100 g P. OO -JCh 14 days
in Maaohinen direction P. W. W. foil
W burns ** oh 37 iagen
in machine direction P. W. W. V c: jpiath 50 days
in machine direction 40 g P. 100 g P W. foil
burns £. nF.ch O days
"" in Maachlnenrichtung > 100 g P. after O days
in cross direction W.

after 21 days *

in MaechiiieiiJL'iohtung

after 0 days in Haschlren direction

after 0 days in the transverse direction

after 15 days

> 150 g P

100 to 250 g of P

foil
burns

foil
burns

^ n tt

ο Ρ

ro

* 50 % Sohrun vaccination «

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The low-temperature shock resistance of the double-layer materials produced according to Example 3 is determined according to the method used at different temperatures? wiä the test wer Sf are determined with values of comparison samples made of a double-layer material made of oriented polypropylene film of the sliding thickness, which do not match the layers from the Mls ^ lii al ;; merisate of ethylene and propylene is provided. The four-layer laminate samples are gealfroit for next 5 days at -30 ° C, while the rest of the samples are kept at Κβ ·: ιγ§πι ~ temperature before the investigation. Both the cold-aged samples and the unaged samples are then tested for their impact resistance at TersoMede: if-r temperatures. ? DIs Έ: _£: e bn: i se are the following:

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Table III Resistance of double-layer materials and comparative samples E

made of a double oriented polypropylene film ^Q

Test temperature, ⁰ C 22.2 17.78 28.89 54.44 40.0 ^w

Double weave according to example 3

in the cold 12.4 * 7.5 5.8 4.4 1.6

^ aged at 22.35 μ ** at 23.62 μ at 23.37 μ at 23.11 μ at 23.62 μ

2 unaged 12.5 7.4 5.7 3.4 1.6

J £ at 22.35 μ at 22.86 μ at 21.6 μ at 22.6 μ at 22.1 μ

αϊ KontrolX double film -

i ¹ in the cold 6.4 5.5 1.9 2.1 1.3

aged at 22.6 μ at 23.88 μ at 23.62 μ at 23.88 μ at 24.9 μ

unaged 8.2 5.1 1.7 1.6 1.2

at 24.38 μ at 23.88 μ at 22.86 μ at 23.11 μ at 24.13 μ

* kg ο cm. ** Exact Dioke or foil sample.

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It follows that the erfindungsgeaässe Schichtatoff is significantly improved based on oriented polypropylene film hineiehtlxe ι its heat sealability and its other mechanical properties.

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Claims (1)

Claims 1. Hoiss-sealable laminate consisting of an oriented Polypropylene film and at least one without a binder firmly adhering, heat-sealable thermoplastic Layer, characterized in that the thermoplastic Layer of one of 2 to 6 wt. Ethylene and 98 to 94 - # Propylene produced copolymer consists. 2c. Laminate according to Claim 1, characterized in that it has a thickness of more than 2.5 µm and the proportion of Ktschpolymerieatoicht in this thickness is at least 5 1 » . 3c laminate according to claim 1 and 2, characterized in that that it has a thickness of 2.5 μ to 0.5 mm and the proportion the mixed polymer layer at this thickness from 5 to 15 pounds amounts to. 4. Laminate n ** h. Claims 1 to 3, characterized in that on "eider Z .iten ύ-äv oriented polypropylene film ^ e Οίίύ NBOC 122 o a layer of the thermoplastic copolymer adheres, and that the proportion of the total thickness of the laminate made up of the polypropylene film is 70 to 90 $ and that of each of the two copolymers is 5 to 15 $ . 5ο laminate according to claim 4, characterized in that it from a large number of concise slides oriented polypropylene and a corresponding number of Intermediate and outer sens chi ent s made of the thermoplastic copolymer. 6. Laminate according to claim 1 to 5, characterized in that the base film made of polypropylene and the mixed polymer layer or layers are biaxially oriented. 7. Laminate according to claim 1 to 6, characterized in that the thermoplaetisohen Mischpolymerisatschichten consist of a product obtained from 2.8 to 3.8 wt. ~ £ ethylene and 97.2 to 96.2 wt 4> Polypropylene copolymer " - 2 ~ BAD ORiQiNAL 109835/1588