FI106008B - Biaxially oriented collapsible polypropylene film with improved sealing properties - Google Patents

Description

1 106008

Biaxially oriented polypropylene seam film with improved barrier properties

The invention relates to a co-extruded multilayer polypropylene film as defined in the claims, which has improved barrier and water vapor and oxygen permeability properties, while having good gliding properties and low shrinkage values to ensure good machine running and compression.

EP-A-0 247 898 (= US-A 4 921 749) discloses a particular polypropylene film which is said to have good sealing strength as well as improved barrier properties. The film according to the invention has advantages over the film disclosed in EP-A-0 247 898, especially with regard to the serviceability of the machines, in high-speed packaging machines, and with regard to heat-blocking. Machinability ·, refers to the applicability of the film in 20 major stroke packing machines. In this case, the film must not be · · ·. too smooth and not too rough, otherwise congestion may occur before the surgery. The rigidity of the film is also • important for this purpose. The effect of heat on the bumps is to understand before ·. *: 25 all the adhesion of objects wrapped in foil by the action of heat. The smaller the · · · infection at elevated temperature, the better the relationship to heat-induced clumps.

* «·

DE-A 35 35 472 (= US-A 4 786 533) discloses polypropylene films having a resin in the backing layer. In particular, the membranes shown therein ·: ··! however, the barrier properties are not yet satisfactory, so there was a need to provide films that were improved for this property.

DE-A 38 14 942 discloses polypropylene films having a resin content of 5 to 2 106008 40% by weight with a softening point of the resin in the range of 80 to 125 ° C. These films are used as shrink labels and exhibit drawbacks with regard to the water vapor and oxygen barrier effect. Moreover, compared to the films of the invention, more layers are formed on the rolls.

It is an object of the present invention to provide a polypropylene film which has improved barrier properties in terms of water vapor as well as oxygen permeability, while having good sliding properties and low shrinkage values.

Thus, the present invention relates to a low shrink sealable film, characterized in that it has: 1) a base layer comprising: 15 polypropylene and a hydrocarbon resin having a softening point of 140 ° C or higher selected from the group consisting of petroleum resins , styrene resins, cyclopentadiene resins *. __ and terpene resins, and 2) at least · one coating layer comprising: • · · '. a) an ethylene / propylene copolymer having an ethylene content of not more than 10% by weight, or • · · · · · b) a propylene / butene (1) copolymer or * c) a propylene / ethylene / α-olefin terpolymer «·« V; Or (d) a mixture of two or more co-polymers or terpolymers mentioned in (a), (b) and (c), · ***; with a thickness of the coating layer (s) of from about 0.4 to about 1.0 μιη and of the coating layer (s) containing at least one anti-tacking agent; · * With a particle size of 1 to 6 μπι, ·; · *: each film obtained by elongating at 100-120 ° C at a stretch ratio of 4-6 '• «and transversely at 130-150 ° C at stretch-35 greater than 7.5.

106008 The butene (1) content of the propylene / butene (1) copolymer according to item 2 (b) is preferably 10 to 15% by weight (based on the copolymer) or the propylene / ethylene / a according to item 2 (c) in the coating layer (s). The α-olefin of the -5 olefin terpolymer preferably has 4-10 carbon atoms, with butene, pentene and hexene being particularly preferred.

The above-mentioned topcoat (s) according to a), b), c) and d) may optionally contain an additional hydrocarbon resin and the undercoat and / or topcoat (s) contains at least one anti-infectious agent and optionally one or more antistatic agents. and / or antioxidant and / or lubricant.

The terpoly-15 monomer of step 2c) of the topsheet (s) preferably comprises 93.2 to 99.0% by weight of propylene, 0.5 to 1.9% by weight of ethylene and 0.5 to 4.9% by weight of a-olefin (% by weight refers to the total weight of the terpolymer).

·. The base layer of the multilayer film consists of a propylene polymer having a melting point of 161-168 ° C.

· ·

Isotactic polypropylene having 6% by weight or less soluble in n-heptane is preferred polypropylene. The polypropylene melt index of the base layer is generally 1.5 to 5 g / 10 minutes at a load of 21.6 N and a temperature of 0:25 at 230 ° C (DIN 53 735).

The low molecular weight carbon -: ***: hydrocarbon resin in the substrate is a natural or synthetic resin • · φ

. ** ·. having a softening point> 140 ° C (measured DIN

According to ASTM E-28) and having 1 »· *;] · 30 in an amount of 5 to 30% by weight, preferably 10 to 20% by weight. · ♦ · * (based on the total weight of the base layer).

Surprisingly, it has been found that the addition of a resin having said softening point (> 140 ° C) substantially improves the water vapor barrier property of the film, thereby simultaneously improving the optical properties of the film and, additionally, its shrinkage behavior. Furthermore, when using films according to invention 4 106008, there is no or less deposition on the rolls, e.g. in the case of longitudinal stretching. Furthermore, the film according to the invention has proved to be particularly suitable for sliding properties, particularly for high-speed packaging machines. The surface of the film is smooth enough not to cause "slip-stic effects", i. not to cause uneven passage through the machine. On the other hand, it also has the necessary height so as not to cause congestion before the stem-10 surgery.

These low molecular weight hydrocarbon resins are selected from the group consisting of petroleum resins, (petroleum) resins, styrene resins, cyclopentadiene resins, and terpene resins, the resins of which are described in Ull-15 manns Enzyklopädie der Techn. Chemie, 4th Edition, Volume 2, pages 539-553.

Petroleum resins are hydrocarbon resins made by low temperature polymerization *. deep-decomposed petroleum catalyst *. In the presence of 20 r. These petroleum substances generally contain • i * *. resin-forming agents such as styrene, methyl-η-styrene, vinyltoluene, indene, methyl-indene, • · butadiene, isoprene, piperylene and pentylene. Styrene resins are small molecules of styrene homo- copolymers of monomers such as α-methylstyrene, vinyltoluene and butadiene Cyclopentadiene resins are · '**; These resins are prepared by keeping substances containing cyclopentadiene at high temperature for a long *; **: Depending on the reaction temperature, dimers, trimers or oligomers may be obtained.

««

Terpene resins are those of terpenes, i. polymers of the hydrocarbons of the formula C10H1635, which terpenes are present in almost all essential oils of plants and oil resins, and phenol-modified terpene resins. Specific examples of terpenes include α-pinenes, β-pinenes, dipentene, limonene, myrene, camphene and the like. The hydrocarbon resins 5 may also be so-called modified hydrocarbon resins. Modification generally occurs as a result of the reaction of the raw material prior to polymerization, the addition of specific monomers, or the reaction of the polymerized product, in particular hydrogenation or partial hydrogenation.

Further, as hydrocarbon resins, styrene homopolymers, styrene copolymers, cyclopentadiene homopolymers, cyclopentadiene copolymers and / or terpene polymers having a softening point of> 140 ° C in each case (hydrogenated product is preferred) are preferred. Cyclopentadiene homopolymers having a softening point> 140 ° C are particularly preferred in the backing layer.

·. If the coating layer (s) also contains hydrocarbon resins, the resins listed above for the base layer may be used. In this case, however, resins which are softened may also be used.

III

: ** melting point <140 ° C.

***** '' In order to further improve certain properties of the film according to the invention, both the backing layer and the top layer (s) may contain suitable additional: ***; agents in appropriate amounts, preferably antistatic agents and / or antioxidants.

• · ·

Preferably, the anti-static agents are • • · * · [· * 30 rocket and saturated aliphatic, tertiary • · * ··· 'amines having an aliphatic residue of 10 to 20 ·: ··· carbon atoms and two 2 -hydroxy- (C2-C4) -alkyl group, with N-C10-C20-, preferably N-C1-6-alkyl-N ', N "-bis- (2-hydroxyethyl) -amines being particularly suitable.

Preferably, so-called primary antioxidants, i.e., antioxidants, are used as antioxidants. sterols inhibited phenols or secondary amines, but also secondary antioxidants, m.p. for example, thioethers or phosphites or phosphonites or also synergistic mixtures of primary and secondary antioxidants. Such antioxidants are described, for example, in Gächter / Miiller rKunststoff-Additive, Carl Hanser Verlag, 2nd Edition (1983). As an assay, the compounds described below are shown: iO-10 / -s.

R-C-R R "- CH 2 -0 - ^ - CH 2 -CH 2 - ^ Λ - ° H

R \

15V

\ ΛλΓ / 0CH2 \ / cil2 ° \.

CibH37OP. yOC18H37 V: 25 N \ OCH, CH20 • · · • 9 • · · · · · · · · ·

Carboxylic acid amides such as erucic acid amide and stearic acid amide · · · · · · or polydiorganosylsiloxanes are preferably used as lubricants.

Suitable anti-caking agents include, for example, organic polymers such as polyamides, polyesters, polycarbonates and the like, or inorganic materials such as silicates, silica and calcium carbonate, which are incompatible with the raw material of the topcoat. .

7 106008

Inorganic substances, in particular silica having an average particle size of 1 to 6 μπι, have proved to be particularly suitable anti-caking agents. The amount of these anti-caking agents is 0.1 to 1% by weight, preferably 0.15 to 0.5% by weight, based on the weight of the topcoats.

The preferred thickness of the topsheet (s) is between 0.4 and 1.0 µιη.

According to the invention, the films described above are molded according to the method defined in claim 17.

In preparing the films of the invention, the longest stretching is carried out at a temperature between 105 ° C and 120 ° C and a stretch ratio of 4-6. The transverse stretching is performed at a temperature in the range of 130-150 ° C. The stretch ratio in the transverse direction is greater than 7.5 and is preferably between 8 and 11. After stretching in the transverse direction of the film ·. performing the attachment step terminating the treatment. Here

The film is further passed at a temperature of 5 to 50 ° C

• · · below the stretching temperature in the tensioning frames, possibly slightly tapering. The convergence during the attachment step • · · • · * is preferably 5 to 15%. The printability of the film is achieved by conventional surface treatments prior to winding V * 25, e.g., by flame treatment or electronic corona treatment. For corona treatment, which can be performed according to any known method, the process is suitably carried out by passing the membrane between two conductor elements acting as · · · electrodes, where such a high voltage - most * · * ··· 'as AC voltages of approximately 10,000 V (with a periodic:: · · · · VV of about 10,000 Hz) are developed such that jets or corona discharges can occur. . Due to jets or corona discharges, • the air above the membrane surface is ionized and bound to molecules on the membrane surface 35 to form polar depositions in a substantially non-polar polymer matrix. The treatment intensities are then within the usual range, with treatment intensities between 38 and 42 mN / m being preferred.

The invention is further illustrated by the following 5 examples (see Table 1 for a comparison of examples).

Example 1

By coextrusion and subsequent biaxial stretch orientation, a three-layered transparent film having a total thickness of 20 μπι was prepared. Each topsheet had a thickness of 0.6 μιη (a film was prepared with a layer order of ABA, with A representing the topsheet and B being the underlayer).

The backing comprises polypropylene supplemented with 10% by weight of resin (ESCOREZ® ECR 356, Exxon, Darien, Connecticut, USA; resin softening point was 140 ° C) based on the total weight of the mixture. The polypropylene used had a melt viscosity of 3.5 g / 10 minutes as determined by DIN

·. 53,735 according to a load of 2.16 kg.

The coating layers consisted of propylene-ethylene. a copolymer having an ethylene content of 4.8% by weight, and added with 0.8% by weight of polydimethylsiloxane, with a 0.13% by weight phenolic stabilizer (Antioxidant 330, * * trade name Ethyl Corp.). , Brussels, Belgium or Baton Rouge, LA, ··· *. ♦ · 25 USA), 0.075% by weight of calcium stearate, as well as 0.33% by weight of SiC> 2 with an average particle size of ***; 2 μπι. Kinematic viscosity of polydimethylsiloxane • · ·. ***. was 30,000 mm 2 / sec; the propylene-ethylene copolymer had a melt viscosity of 6.0 g / 10 min, measured according to DIN 53735 • · · '· * · * 30 at a load of 2.16 kg.

··· • ·

Example 2 A film was prepared as described in Example 1, although the proportion of resin in the base layer was 20% by weight (the same resin as in Example 1 was used).

9 106008

Example 3

A film was prepared as described in Example 1, although the proportion of resin in the backing layer was 30% by weight (using the same resin as in Example 1).

Example 4

A membrane was prepared as described in Example 2, although now using the structure ABC, with the A side being subjected to corona radiation treatment and free of polydimethylsiloxane (B layer = base 10 layer).

Example 5

A film was prepared as described in Example 2, now using the structure ABC, whereby the C overlay was made from a mixture of ethylene-15-propylene copolymer with 10% by weight of resin (the same resin as in Example 1 was used). Comparative Example 1

A film was prepared as described in Example 1, but without the addition of the resin used in Example 1.

• · · 20 Comparative Example 2 • · · ♦ · · •. The film was prepared as described in Example 2, but using a resin having a resin softening point of 85 ° C (ESCOREZ® 5380, Exxon, Darien, Connecticut, USA).

• «· 1:: 25 Comparative Example 3

A membrane was prepared as described in Example 2, ***. la, which, however, had no «« »film layers. ·· *. SiC> 2.

··· The properties determined were evaluated by the following equation (see Table 1): ++ = excellent (ie no resin coatings on rollers) + = very good (ie hardly resin coatings) - = poor (ie already significant resin coatings) - = very poor (ie clear resin coatings), or the rating was reported as numerical values.

10 106008

It is clear from Table 1 that the films according to the invention are superior to the reference films (reference examples) in terms of the desired feature image.

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12 106008 Thermal Loss Determination To measure the thermal leaching, two blocks of 72 mm x 41 mm by 5 x 13 mm covered with one side of a blanket are wrapped in a film to be measured. Wood blocks placed on top of each other with their felt coatings are placed on a 200 g weight and this structure is placed in an oven preheated to 70 ° C for 2 hours. It is then cooled to room temperature (21 ° C) for 30 minutes, the weight is removed from 10 wooden blocks and the upper block is lifted from the lower block by mechanical means. The assessment is based on four individual measurements to determine the maximum shear force (measured as N). The requirement is met if none of the individual measurements exceed 15 5 N.

Determination of opacity

Membrane opacity is measured by ASTM-D 1003-52, using · instead of 4-degree hole opener. 1 degree slit dimmer and opacity are expressed as • 20% of the four overlapping layers of film. Four * * '. The layer is selected because an optimal measuring range is used. The evaluation of opacity follows the following scale: ♦ * · ”· <15% = very good I · '! 25> 15% = average> 25% = poor · *** · Gloss ♦ ♦♦. ***, Gloss is determined in accordance with DIN 67530. The reflection value · ·· # · β is measured as the optical property of the film surface. Based on * · * · * 30 ASTM-D 523-78 and ISO 2813, a 20 ° angle of single beam was used. The beam of light meets a flat test surface at a controlled angle of ♦ j ··· and is reflected or scattered. The light rays striking the photoelectric receiver • * · »· indicate a relative electrical magnitude. The Mit-35 background value is dimensionless and must be reported using the 13th angle of the single thread 106008. The gloss rating (single beam angle 20 °) follows the following scale:> 115% = very good <115 - 100% = average 5 <100% = poor

Determination of shrinkage

Shrinking refers to the percentage change in length (10-1) / 10. Square samples of film having a side length of 10 cm (= 10) are placed for 5 minutes at 10 to 120 ° C. The remaining length 1 is then measured.

Determination of water vapor and oxygen permeability

Water vapor permeability is determined according to DIN 53122 part 2. The oxygen barrier effect is determined in accordance with Scheme 15 DIN 53380 Part 3 with a humidity of 53%.

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Claims (17)

A low shrink sealable film, characterized in that it comprises: 5) a base layer comprising: polypropylene and a hydrocarbon resin having a softening point of 140 ° C or higher, selected from the group consisting of petroleum resins, styrene resins, cyclopentadiene resins 10 and terpene resins; and 2. at least one topsheet comprising: a) an ethylene / propylene copolymer having an ethylene content of up to 10% by weight, or b) a propylene / butene (1) copolymer, or 15 c) a propylene / ethylene / α-olefin terpolymer; or (d) a mixture of two or more of the co-or terpolymers mentioned in (a), (b) and (c), having a thickness of the topsheet (s) of: * ··· 0.4 - 1.0 μιη and the topsheet (s) containing 'S ·' (s) containing at least one anti-adhesive having a particle size of 1 to 6 μιη, which film is obtained by performing a longitudinal stretch at a stretch ratio of 100-120 ° C at a stretch ratio of 4-6 ° and a transverse direction at a temperature of 130-150 ° C at a stretch ratio greater than 7.5. ... 2. The sealable tongue according to claim 1, characterized in that the butene (1) of the propylene / butene (1) copolymer of (2) (b). content is: Y: 10 to 15% by weight. • ·. ***. The seams according to claim 1 or 2. film, characterized in that the α-olefin in the terpolymer of 2) c) is an α-olefin having • · • «· * '! 4 to 10 carbon atoms. A sealable film according to one or more of claims 1 to 3, characterized in that the α-olefin in the terpolymer of 106008 dan 2) c) is selected from the group consisting of butene (l), pentene (l) and hexene. (l). A sealable film according to one or more of claims 1 to 4, characterized in that the terpolymer according to 2) c) consists of 93.2 to 99.0% by weight of propylene, 0.5 to 1, 9% by weight of ethylene and 0.5 to 4.9% by weight of α-olefin. 6. A sealable film according to one or more of claims 1 to 5, characterized in that the backing layer contains 5 to 30% by weight of a hydrocarbon resin. A sealable film according to claim 6, characterized in that the base layer contains 10 to 20% by weight of hydrocarbon resin. A sealable film according to one or more of claims 1 to 7, characterized in that the coating layer (s) contain a hydrocarbon resin. ; '·· 20 A sealable film according to claim 8, characterized in that the top layer or top layers comprise a hydrocarbon resin of 5 to 30% by weight by weight. amount of rye. • «• · The weldable wax according to claim 9, characterized in that the coating layer (s) contain 10 to 20% by weight of hydrocarbon resin. A sealable film according to one or more of Claims 8 to 10, characterized in that the hydrocarbon resin of the 30 or more layers is an intermediate. a group consisting of petroleum resins, styrene resins, cyclopentadiene resins and terpene resins. The seamable fiber according to claim 11, characterized in that the hydrocarbon resin is a cyclopentadiene resin. ie 106008 A sealable film according to one or more of claims 1 to 12, characterized in that the topsheet (s) comprise one or more antistatic agents and / or antioxidants and / or lubricants. A sealable film according to one or more of claims 1 to 13, characterized in that the base layer contains one or more antistatic agents and / or antioxidants and / or lubricants. 14 106008 Claims t A sealable film according to one or more of claims 1 to 14, characterized in that the film has one backing layer and two topsheets. Use of a sealable film according to one or more of claims 1 to 16 as packaging material. 15 17th A process for producing a low shrink sealable film comprising a backing layer comprising polypropylene and a hydrocarbon resin having a softening point of 140 ° C or higher selected from the group consisting of petroleum resins, styrene resins, cyclopentadiene resins, and , and least • ««; a coating comprising: (a) an ethylene / propylene copolymer having an ethylene content of not more than 10% by weight, or; C) propylene / ethylene / α-olefin terpolymer or d) a mixture of two or more of the co-or terpolymers mentioned in a), b) and c); Wherein the topsheet and / or backing layer comprises at least one anti-tacking agent and / or glidant, characterized by coextrusion. first forming a precoat in a wide slot nozzle which | ] consists of a backing layer and at least one overcoat, which is then fixed to a cooling roll and then stretched at a longitudinal temperature of 105 to 120 ° C at a stretch ratio of 4 to 6 and transversely at a temperature of 130 to 150 ° C. with a stretch ratio greater than 7.5. • · «* * · · 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ·· 1 ••••••••••••••••• 106008