Coated, monolayer biaxially oriented polypropylene film

Abstract

To provide a very thin polymer film that comprises good optical quality and good barrier properties as well as a good surface metallizability; and a laminate material that has a low polymer content.SOLUTION: The invention relates to a coated, biaxially oriented polypropylene film 110 capable of forming a laminate material having the polypropylene film 110, and a method for producing the polypropylene film 110. The polypropylene film 110 is a monolayer extruded polypropylene film that includes an extruded polypropylene layer 112 and at least one coating 114. The extruded polypropylene layer 112 includes a homo polypropylene and a maleic anhydride side chain type polypropylene. The coating 114 is a dispersion coating comprising polyurethane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coated monolayer extruded biaxial polypropylene film, a method for producing the monolayer extruded biaxial polypropylene film, and a laminate comprising the monolayer extruded biaxial polypropylene film. [Background technology]

[0002] A recent trend in the field of resin packaging technology is to reduce the amount of resin material. When creating sustainable packaging materials, there is a tendency to reduce the amount of resin components in the packaging material, especially packaging laminate materials. Typical packaging laminate materials, for example, comprise a paper substrate and / or a metal layer together with a thin resin film.

[0003] Reducing the resin film thickness is one option to reduce the resin component. This not only reduces the need for raw materials economically, but also makes environmental sense. It can also simplify the recycling of packaging laminates with low polymer content (e.g., <5%) while limiting the amount of extraneous material available. In this case, reducing the film thickness can further reduce the overall layer thickness of the packaging laminate, saving additional raw materials such as paper substrates.

[0004] For example, when using a 15 μm thick resin film in a paper / resin packaging laminate, limiting the amount of foreign material to 5% requires limiting the overall thickness of the packaging laminate to at least 300 μm. Thus, reducing the thickness of the resin film affects the overall thickness of the packaging laminate.

[0005] In some cases, it may be necessary to use multiple extruded resin films (multilayer films) to achieve desired properties. Individual film layers (e.g., 3-7 layers) can be optimized for different properties. For example, the following properties can be achieved by corresponding multiple film layers: - Anti-stick effect (mainly the outer layer), - sealing properties (mainly the outer layer), - Optical properties such as color and gloss, - mechanical properties such as tensile strength, shrinkage etc. (mainly due to the inner and central layers) and - Improved adhesion for post-treatment (outer layer), surface metallization or lamination.

[0006] The desired anti-stick effect is usually achieved through the addition of anti-stick masterbatches or anti-sticking agents to the corresponding thin film layers (mainly outer layers), as known, for example, from Patent Document 1. The anti-sticking agents typically have solid particles with sizes in the μm range (particle size of about 1 μm to 10 μm). The anti-sticking effect allows for reliable and rapid winding and unwinding of the thin film. However, the anti-sticking masterbatches may impair the appearance and / or other thin film properties, such as surface metallization. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] German Patent Application Publication No. 102018101747

[0008] It is also necessary to provide the resin film with sufficient protective properties to allow the formation of a metallized layer. For this purpose, an outer layer is usually formed on a copolymer that forms a metallized layer sufficiently. The individual layers of the film, usually composed of different resins, cannot be separated from each other, making recycling difficult or even impossible. Following the trend toward sustainable packaging, attempts have been made to form metallized layers directly on paper substrates, but these metallized layer attempts have not provided good protective properties. Furthermore, the resulting laminated (film) packaging materials are uneconomical.

[0009] The production of stretched thin films is also known from the technical biaxially stretched polypropylene thin film (e.g. capacitor thin film or current collector thin film) technology, in which forced extrusion is carried out during the stretching of a monolayer thin film, which is called the crystalline transformation technique of the polymer. The crystalline transformation technique is achieved by using expensive high-purity materials and slowly cooling the melt after forced extrusion.

[0010] Crystalline conversion techniques result in the formation of structures called "lassos" in the film, which increase roughness to avoid film stickiness, but slow cooling of the melt can make production slow and uneconomical. Also, the increased roughness can diminish the appearance and protective effect of the film.

[0011] Furthermore, raw materials for technical biaxially oriented polypropylene thin film capacitor films (BOPP-C) should, in principle, contain little or no phosphites due to normal electrical properties. Thus, biaxially oriented polypropylene thin films are only marginally stable, making recycling difficult. Biaxially oriented polypropylene thin film raw materials for packaging applications usually contain high phosphate contents. The phosphate content allows for good recycling of manufacturing waste, particularly film edge scraps, tears, or cuttings.

[0012] In addition, the raw material for biaxially oriented polypropylene capacitor thin films is extremely pure and is about 20% to 30% more expensive than axially oriented polypropylene for packaging. Therefore, the raw material for biaxially oriented polypropylene capacitor thin films is not used for packaging purposes. Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to at least partially limit the above disadvantages, in particular to provide an ultrathin polymer film with good optical properties, good protective properties and good surface metallization, and to provide a laminate material with a low polymer content.

[0014] The object of the present invention is solved by the coated biaxially oriented polypropylene film of the present invention, by the method for producing it and by the laminate material of the present invention. Further features of the present invention are set out in the dependent claims and in the following description.

[0015] In particular, the object of the present invention is achieved by a coated biaxially oriented polypropylene film (BOPP film). The polypropylene film is a monolayer extruded polypropylene film having at least one coated extruded polypropylene layer. The extruded polypropylene layer comprises homopolypropylene and maleic anhydride side chain (chain) polypropylene. The coating layer is a dispersion coating layer comprising polyurethane. [Means for solving the problem]

[0016] Polypropylene (abbreviated "PP") is a partially crystalline resin, a non-polar thermoplastic resin, and part of the polyolefin family. Polypropylene is obtained by polymerization of the monomer propylene. Polypropylene homopolymer (also homopolypropylene, PPH) is obtained by polymerization of pure propylene. For example, polypropylene homopolymer is sold by LyondellBasell under the trade name Moplen HP525J, which has a melt flow rate (MFR) of about 30 g / 10 min, or under the trade name Adstif HA622H, which has a melt flow rate of about 2.0 g / 10 min.

[0017] In another aspect, the polypropylene homopolymer may be an isotactic homopolypropylene having a high degree of isotacticity, for example, the homopolypropylene used has a polymeric tacticity in the range of greater than 70%, greater than 85%, or in the range of 92% to 96%.

[0018] Maleic anhydride side chain polypropylene (PP-g-MAH) is a modified form of polypropylene formed through maleic anhydride (MAH) chemically bonded to the polypropylene chain. Functionalization of polypropylene alters the surface properties of the polypropylene, particularly improving its compatibility with polar materials. For example, Mitsui Chemicals, Inc., produces this product under the trademark ADMER TM (Especially ADMER TM AT1179E, ADMER TM AT3355E, ADMER TM RA206E, ADMER TM AT3177E, ADMER TMMaleic anhydride side chain (grafted) polypropylene sold under the trademark ADMER TM AT1179E was suitable. Maleic anhydride side chain polypropylene agents are also available under the trademarks Modic® (Mitsui Chemicals, Inc.), Plexar® (Chemflex Corporation), Epilene® (Eastman Company), and Bynel® (Dow Company).

[0019] The blend of homopolypropylene and maleic anhydride side chain polypropylene results in surprisingly good coating adhesion, eliminating the need for additional adhesion promoters between the extruded polypropylene layer and the coating layer. The good adhesion is due to the polar components of the single extruded polypropylene layer (single layer).

[0020] By applying a polypropylene layer on only one side, the polar component can improve printability on the second side of the polypropylene layer opposite the coating layer, and can also improve adhesion of the polypropylene film to structural layers (e.g., film or laminate materials).

[0021] Furthermore, a coating containing polyurethane can improve protective properties. Furthermore, it has been found that the properties of surface metallization of polypropylene thin films can also be improved by using a coating layer. For example, by using surface metallization of packaging materials (especially thin film materials or laminated materials with good protective properties and / or good optical properties (glossiness)), they can be used as capacitor thin films (e.g., wound thin film capacitors) or current collecting thin films (e.g., batteries).

[0022] Non-extruded dispersion coatings can achieve extremely thin coating thicknesses. In one embodiment of the present invention, coatings are formed to thicknesses in the range of 50 nm to 150 nm, 80 nm to 120 nm, or 90 nm to 110 nm. Thus, the coating layer constitutes only a small portion of the total thickness of the polypropylene film, for example, in the range of 2 μm to 10 μm, 3 μm to 7 μm, or 4 μm to 6 μm. Such ultra-thin films simultaneously conserve polymer and increase the recyclability of the film or laminate material.

[0023] For example, the trademark TAKELAC TM Aqueous polyurethane dispersions, including a known polyurethane dispersion sold as WPB-341 (Mitsui Chemicals, Inc.), are applied to the coating layer.

[0024] In other embodiments of the present invention, the coating layer comprises nanoparticles. For example, the coating layer may comprise 2% to 20%, 4% to 15%, or 5% to 10% by weight of nanoparticles. For example, the nanoparticles may comprise silicon dioxide (SiO) nanoparticles (e.g., sold under the trademark Levasil® CT4 PL), titanium dioxide (TiO) nanoparticles, alumina (AlO) nanoparticles, iron trioxide (FeO) nanoparticles, iron tetroxide (FeO) nanoparticles, zinc oxide (ZnO) nanoparticles, and / or the like.

[0025] The nanoparticles have an average particle size (equivalent sieve diameter) of 20 nm to 150 nm, 50 nm to 120 nm, or 80 nm to 100 nm. These particle sizes create a surface roughness sufficient to prevent adhesion between polypropylene thin films during winding and unwinding. It has been found that a coefficient of friction (COF value (microseconds) ISO 8295) of the resulting thin film of COF <= 1 allows the thin film to be wound and unwound without any adhesion between the thin films. In particular, when winding the polypropylene thin film, a small amount of air is trapped and retained between each wound layer of the thin film, enabling reliable unwinding of the polypropylene thin film. Therefore, non-adhesive thin film master batches can be produced. In particular, polypropylene thin films are released from non-adhesive master batches of non-adhesive particles with diameters within the film thickness dimension range.

[0026] The use of non-stick thin film prototype lots is advantageous because nanoparticles (particle size as described above) can be selected that are smaller than the non-stick particles typically used in the coextrusion of non-stick thin film prototype lots, thus allowing for the formation of thin film coating layers that are significantly thinner than conventional coextruded skin layers.

[0027] Also, the surface roughness is sufficiently small to result in polypropylene with high optical quality (very low haze values) and / or good protective properties (even in combination with surface metallization). Through the use of nanoparticles, especially for non-bonded particles coextruded through the coating layer, the properties and quality of the surface metallization can be improved.

[0028] Furthermore, the nanoparticles (non-adhesive or non-adhesive particles) do not damage the surface-metallized polypropylene film during winding and unwinding of the film, particularly avoiding the formation of pinholes that occur when relatively large solid particles in known anti-adhesion layers are pressed into the metal layer during winding of the film.

[0029] In another aspect, the extruded polypropylene layer (single layer) is composed of homopolypropylene and maleic anhydride side-chain polypropylene, and the maleic anhydride side-chain polypropylene content of the extruded polypropylene layer is at least 10 wt%, at least 15 wt%, or at least 20 wt%, and the maleic anhydride side-chain polypropylene content of the extruded polypropylene layer is at most 35 wt%, at most 30 wt%, or at most 25 wt%.

[0030] By combining maleic anhydride side-chain polypropylene with homopolypropylene, a high production rate can be achieved even with a single-layer extruded polypropylene layer (single layer). Slow cooling of the extruded melt - in the case of thin film formation accompanied by crystalline transformation - is not necessary. Despite the high production rate, the polypropylene thin film has a thickness range of 2 μm to 10 μm, 3 μm to 7 μm, or 4 μm to 6 μm. In addition, the polypropylene thin film has a density of 0.9 g / cm. 3 ~0.95g / cm 3 , especially 0.91 g / cm 3 ~0.93g / cm 3 It has.

[0031] Furthermore, since polypropylene thin films can be produced with extremely small thickness deviations, capacitor thin films, current collecting thin films, and / or packaging thin films (or packaging laminate films) can be produced. The thickness of the polypropylene thin film can have a desired thickness tolerance (allowable range) of ±0.4 μm, ±0.25 μm, or ±0.12 μm (for production lengths of 100 m or more).

[0032] The coating layer may also be a water-soluble coating layer or a substantially water-dispersible coating layer. The substantially water-dispersible coating layer contains a solvent content of up to 5% by volume (when applied). The water-soluble coating layer or substantially water-dispersible coating layer conserves solvent and improves burst protection. For example, the coating layer may be a coating layer sold under the trade name TAKELAC by Mitsui Chemicals, Inc. TM Contains WPB-341 (polyurethane).

[0033] In another aspect, a metal coating layer can be disposed on the coating layer (particularly directly on the coating layer). Surface metallization can be disposed on one or both sides of the polypropylene film as well as the coating layer.

[0034] The metal coating layer may comprise aluminum, zinc, titanium, gold, silver, silicon, copper, chromium and / or other metals, alloys thereof or compounds thereof. Similarly, the metal coating layer may comprise oxides of said elements, in particular aluminum oxide (AlO x ) and / or silicon oxide (SiO x ) or compounds thereof. In particular, the metal coating layer may comprise a plurality of (different) metal coating layers. In the metal coating layer of the thin film for packaging, aluminum or aluminum alloys have shown good protective properties. In particular, they can form a good moisture barrier layer.

[0035] In the illustrated polypropylene film, a coating layer is formed on a first side of the polypropylene layer. A second, opposite side of the polypropylene layer is surface treated without a coating layer. For example, the surface treatment can be a corona surface treatment and / or a plasma surface treatment. This can improve the adhesion of the polypropylene film to a structural layer (e.g., a paper substrate) and can also improve printability. Furthermore, the surface of the polypropylene film can be treated before the coating layer (e.g., plasma treatment or corona treatment) is applied.

[0036] The object of the invention is also achieved by a laminate, in particular a laminate for food packaging, which comprises at least a polypropylene film of the type described above as well as a structural layer, the polypropylene film being arranged, in particular laminated (directly) on the structural layer, the structural layer being a paper substrate itself or formed from a paper substrate.

[0037] If the metallization layer is formed on the polypropylene film, the metallization layer faces the structural layer (the metallization layer is disposed between the structural layer and the structural layer). Alternatively, the polypropylene layer can be formed as the structural layer with the metallization layer facing outward.

[0038] The polypropylene film content in the laminate can be configured to be up to 5% by weight, up to 4% by weight, or up to 3% by weight to improve recyclability. Low polymer content also saves raw materials.

[0039] The object of the present invention can also be achieved by a method for producing the monolayer extruded polypropylene film, which comprises the following steps: - extruding an extruded polypropylene layer (single layer) comprising monopolypropylene and maleic anhydride side chain polypropylene; - coating, in particular inline coating, of the extruded polypropylene layer with a coating layer comprising a water-soluble dispersion, optionally nanoparticles and polyurethane, and - stretching the polypropylene layer, which may include stretching the polypropylene layer in the machine direction (by an MDO machine) and / or stretching the polypropylene layer in the transverse direction (by a TDO device).

[0040] Also, the machine and transverse stretching can be carried out simultaneously or sequentially. A coating layer can be provided on a polymer film that has already been stretched in both the machine and transverse directions, i.e., biaxially stretched. Similarly, a coating layer can be formed before the stretching step.

[0041] First, the polymer film can be stretched in only one direction (e.g., the machine direction in an MDO apparatus). Next, a coating layer can be formed on the polymer film stretched in one direction (e.g., the machine direction). The coated polymer film can then be stretched in a second direction (e.g., the transverse direction in a TDO apparatus). For example, the polymer film can be first stretched in the machine direction, then coated, and subsequently stretched in the transverse direction. In this way, a stretching step can be performed before and / or after coating.

[0042] The resin melt is usually extruded through a slot die called a chill roll. The extruded resin melt, i.e., the polypropylene layer, is guided through the chill roll before stretching. The chill roll is usually made of a heat-conductive material and is maintained at a low temperature by an internal cooling device (water or other coolant). For example, the temperature of the chill roll is maintained at 35°C to 45°C or 38°C to 42°C. The resin melt that comes into contact with the chill surface of the chill roll begins to rapidly cool and harden into a rigid strip.

[0043] For example, the melt can be selectively guided through a water bath in the temperature range of 20° C. to 35° C. or 22° C. to 28° C. to further accelerate the cooling of the melt, allowing for faster production of thin films. While the use of a water bath is not required for the production of polypropylene or coated polypropylene thin films, it has been found that the use of a water bath allows for more rapid and uniform cooling.

[0044] The polypropylene layer can be coated by roller coating, spray coating and / or curtain coating, among others. Surface coating can be carried out in particular in the stretching apparatus where the stretching step is carried out. In another embodiment of the invention, the coating can be carried out by reverse kiss coating, where the extruded (and stretched) polypropylene layer is guided by a guide roller, and a coating roll rotates in the conveying direction on the side opposite the polypropylene layer. The coating roll, to which the aqueous dispersion is applied, transfers the dispersion to the polypropylene layer and applies it. This allows the liquid dispersion to be applied particularly uniformly at very high processing speeds.

[0045] The solid content of the liquid dispersion (polyurethane particles, optionally nanoparticles and / or others) is 5% to 20% by weight or 10% to 15% by weight (based on the total mass of the liquid dispersion). The wet layer formed by the liquid dispersion has a weight per unit area of, for example, 3 g / m. 2 ~20g / m 2 or 6 g / m 2 ~10g / m 2 The polypropylene layer can be pretreated with a wetting agent and / or mixed with an aqueous dispersant (content of up to 0.5% by weight or up to 0.3% by weight) to improve the wetting of the polypropylene layer by the dispersant. A possible wetting agent is, for example, an ethoxylated acetylenic surfactant sold under the trademark Surfynol® 440 by Evonik.

[0046] Furthermore, the machine direction stretching step (e.g., using an MDO device) can be carried out at a temperature range of 90°C to 120°C or 95°C to 112°C. The machine direction stretching can be carried out at a stretch ratio range of 4 to 6 or 4.5 to 5. The transverse direction stretching step (e.g., using a TDO device) can be carried out at a temperature range of 140°C to 190°C or 150°C to 185°C. The transverse direction stretching can be carried out at a stretch ratio of 4 to 10, 5 to 9, or 6 to 9.

[0047] The polypropylene thin film produced is usually a biaxially oriented polypropylene thin film. The conveying (line) speed of the polypropylene thin film (production speed after the stretching step) is, for example, 40 m / min to 55 m / min or 45 m / min to 50 m / min (depending on the test equipment). The conveying speed in industrial production processes is at least 300 m / min, at least 400 m / min, at least 500 m / min, at least 600 m / min, at least 700 m / min, or at least 800 m / min.

[0048] For example, a coating may be applied to one or both sides of the polypropylene layer. The manufacturing process may also include a surface treatment step of corona and / or plasma treatment on the side of the polypropylene layer opposite the coating layer to improve adhesion of the polypropylene film to a structural layer (e.g., a paper substrate). Printability and / or surface metallization may also be improved.

[0049] The process of the present invention comprises the following steps: a surface metallization step in which a material containing aluminum, silicon, copper, zinc, titanium, gold, silver, chromium and alloys thereof and / or oxides thereof is disposed on the coating layer; - Laminating a thin polypropylene film onto a structural layer of or containing a paper substrate. [Brief explanation of the drawings]

[0050] The embodiments of the present invention will be described in detail with reference to the accompanying drawings below. [Figure 1] Cross-sectional view showing the structure of a polypropylene thin film according to the present invention [Figure 2] Cross-sectional view showing the structure of the polypropylene thin layer of the present invention having a coating layer. [Figure 3] Block diagram showing the steps that make up the manufacturing process DETAILED DESCRIPTION OF THE INVENTION

[0051] 1 is a cross-sectional view showing the structure of a polypropylene thin film 110 according to the present invention. The thickness of the polypropylene thin film 110, the polypropylene layer 112 and the coating layer 114 as well as the nanoparticles 115 are not shown to scale.

[0052] The biaxially oriented polypropylene film 110 has a single extruded polypropylene layer 112 and at least one cover layer 114. In the illustrated example, the cover layer 114 is disposed directly on the extruded polypropylene layer 112.

[0053] The polypropylene layer 112 includes homopolypropylene and maleic anhydride side chain polypropylene, and the maleic anhydride side chain polypropylene and homopolypropylene in a content of at least 10 wt%, at least 15 wt%, or at least 20 wt%, are extruded, for example, as a mixture.

[0054] The coating layer 114 is a dispersed coating layer applied as an aqueous dispersion onto the extruded polypropylene layer 112. The illustrated coating layer 114 includes polyurethane (PU) and nanoparticles 115 (e.g., silicon dioxide (SiO2) nanoparticles). The dried coating layer 114 has a thickness ranging from 50 nm to 200 nm, 80 nm to 180 nm, or 100 nm to 150 nm. The nanoparticles 115 have an average particle size ranging from 20 nm to 150 nm, 50 nm to 120 nm, or 80 nm to 100 nm, for example. The nanoparticles impart a surface roughness to the polypropylene thin film 110 that prevents adhesion between the polypropylene thin films 110 when the film is wound and unwound. The use of a prototype lot of anti-adhesion thin film between the polypropylene thin films 110 is not necessary.

[0055] The illustrated polypropylene film 110 can have a thickness in the range of 2 μm to 10 μm, 3 μm to 7 μm, or 4 μm to 6 μm. Thin polypropylene films in the range of 2 μm to 6 μm are also particularly good.

[0056] A metal coating layer 116 shown in FIG. 2 can be formed on the coating layer 114 of the polypropylene thin film 110. The metal coating layer 116 includes aluminum, silicon, copper, zinc, titanium, gold, silver, and alloys thereof. The metal coating layer can also be formed of an oxide, particularly aluminum oxide (AlO x ) and / or silicon oxide (SiO x In particular, for packaging applications, metal layers of aluminum and aluminum alloys are particularly suitable, for example as moisture barrier layers. For thin film capacitor applications, aluminum / zinc alloys can be used in particular.

[0057] Additionally, a polypropylene film 110 (either surface metallized or non-metallized) can be applied to the structural layer 120 to provide the laminate 100 .

[0058] The metallization layer 116 can be oriented toward the structural layer 120 (as shown) and the polypropylene film 110 can be attached to the structural layer 120. In this case, the metallization layer 116 is positioned between the structural layer 120 and the cover layer 114. Alternatively (not shown), the metallization layer 116 can be positioned remotely from the structural layer 120. If the polypropylene film 110 is not surface metallized, the cover layer 114 can be positioned directly or indirectly against the structural layer 120.

[0059] If the polypropylene film 110 is in contact with the structural layer 120 without the metallized layer 116 or if the metallized layer 116 is offset from the structural layer 120, a surface treatment (particularly a corona or plasma treatment) can be applied to one side of the polypropylene film 110 facing the (uncoated) structural layer 120. The surface treatment can improve the adhesion of the polypropylene film 110 to the structural layer 120, e.g., a paper substrate.

[0060] In the illustrated embodiment, the polypropylene thin film 110 can be formed to a thickness in the range of 2 μm to 10 μm, particularly 2 μm to 6 μm, and the structure layer 120 can be formed to a maximum thickness in the range of 40 μm to 200 μm, particularly 40 μm to 120 μm.

[0061] The content of polypropylene film 110 in laminate 100 can be selected to be up to 5 wt%, up to 4 wt%, or up to 3 wt%, and the thickness ratio of polypropylene film 110 to the maximum thickness of structural layer 120 can be selected.

[0062] 1 and 2 show a polypropylene layer 112 that is coated or metallized on one side. It is possible to obtain a polypropylene film 110 that coats both sides of the polypropylene layer 112 and optionally forms a metal layer on both sides.

[0063] FIG. 3 shows a process flow for manufacturing a monolayer extruded polypropylene film 110 or laminate 100 similar to FIGS.

[0064] The method 1000 for making the laminate 100 includes the step 1100 of extruding a polypropylene layer 112 (single layer). The extruded polypropylene layer 112 comprises homopolypropylene and maleic anhydride side chain polypropylene, preferably extruded as a blend.

[0065] After the extrusion step 1100, the polypropylene layer 112 may be stretched (eg, by an MDO apparatus) by a stretching step 1150, which includes a machine direction stretching step.

[0066] After the longitudinal stretching step 1150, the polypropylene layer 112 is coated with an aqueous dispersion containing polyurethane and, optionally, nanoparticles in a coating step 1200. The coating step 1200 is particularly directed (e.g., by reverse kiss coating). After the coating step 1200, the polypropylene layer 112 can also be further stretched in the transverse direction (step 1250). After the aqueous dispersion has dried, a coating layer 114 can be disposed on the biaxially oriented polymer film (FIG. 1).

[0067] Alternatively, the coating layer can be applied before or after the stretching step, especially before simultaneous stretching in the machine and transverse directions.

[0068] Additionally, in step 1400, the surface of the cover layer 114 can be metallized to form a metal layer 116. Additionally, a polypropylene film 110 can be laminated (step 1500) onto the structural layer to form the cover material. [Example]

[0069] Example 1

[0070] In the thin film manufacturing method of the present invention (Example 1), homopolypropylene (trademark: Moplen HP 525J) and maleic anhydride side chain polypropylene (trademark: ADMER TM The homopolypropylene content was approximately 90% by weight, and the maleic anhydride side chain polypropylene content was approximately 10% by weight.

[0071] The resin melt was extruded through a grooved die on a chill roll. The temperature range of the twin-screw extruder was 240°C to 260°C, and the temperature of the chill roll was approximately 40°C. In the cooling process, the extruded resin melt was guided into a water bath with a temperature range of 28°C to 32°C. Then, machine direction stretching and transverse direction stretching were performed at a machine direction stretch ratio of 4 to 5. The production speed of the biaxially oriented polypropylene thin film in the test equipment was 45 m / min to 50 m / min. This resulted in a polypropylene thin film with a thickness of 6.1 μm (deviation ±0.16 μm).

[0072] A typical scale of the test equipment transport speed to industrial production allows industrial production speeds of at least 300 m / min, at least 400 m / min, at least 500 m / min, at least 600 m / min, at least 700 m / min or at least 800 m / min. The scaling factor (industrial transport speed / test equipment transport speed) was regularly between 5 and 20.

[0073] The dispersion coating layer was applied by reverse kiss coating directly onto the machine direction stretched polypropylene layer (and therefore before transverse stretching). The dispersion was a polyurethane dispersion manufactured by Mitsui Chemicals, Inc. under the trade name TAKELAC. TMIt contained WPB-341 and nanoparticles brand name Nouryon CT4-PL (5 wt % in the dispersion).

[0074] The polypropylene layer was corona treated before the coating process. The solids content of the polyurethane dispersion was 10%-15%. This resulted in a dry coating layer thickness ranging from 100 nm to 150 nm.

[0075] The polypropylene thin film had good friction properties (a COF value of 0.67 according to International Standard 8295 for Coefficient of Friction of Resin Thin Films) and good optical properties (a haze value of 0.86 according to American Society for Testing Materials D1003), which prevented blocking. Furthermore, good adhesion of the coating layer to the polypropylene thin film was achieved (the tape adhesion test was passed). Example 2

[0076] For the thin film manufacturing method according to the present invention (Example 2), homopolypropylene (trade name: Adstif HA 622 H) and maleic anhydride side chain polypropylene (trade name: ADMER TM The mixture containing the homopolypropylene and the maleic anhydride side chain polypropylene was extruded as a single layer. The homopolypropylene content reached about 80 wt % and the maleic anhydride side chain polypropylene content reached about 20 wt %.

[0077] In the extrusion process, the resin melt was extruded through a grooved die on a chill roll. The temperature range of the twin-screw extruder used was 240°C to 260°C, and the temperature of the chill roll was approximately 40°C. For further cooling, the extruded resin melt was guided through a water bath with a temperature range of 25°C to 30°C. It was then stretched in both the machine direction and the transverse direction with a machine direction stretch ratio range of 4 to 5. The production speed of the biaxially stretched polypropylene thin film was in the range of 50 m / min. This resulted in a polypropylene thin film with a thickness of 4.0 μm (deviation ±0.10 μm). The resulting coating material is designated Example 1.

[0078] The obtained polypropylene thin film had good optical properties (haze value according to American Society for Testing and Materials D1003: 0.90) and good friction properties (COF value according to International Standard 8295 for Coefficient of Friction of Thin Resin Films: 0.95), and was able to avoid blocking. The table below shows a summary of Examples 1 and 2 according to the present invention, and Comparative Examples 3 to 6.

[0079] [Table 1] PP: Polypropylene PU: Polyurethane M: Moplen HP 525J Ads:Adstif HA 622 H ADM:ADMER AT1179E B: Borealis HC300BF Comparative Example 3

[0080] Comparative Example 3, which was produced based on Example 1, did not have a coating layer. The friction properties were significantly improved (COF value = 1.42 μs), but stickiness occurred. Compared to Comparative Example 3, Example 1 of the present invention has the advantage of having a coating layer that does not impair optical properties. Comparative Example 4

[0081] In Comparative Example 4, high-purity polypropylene (capacitor-grade polypropylene, highly crystalline polypropylene homopolymer) was extruded. Maleic anhydride side-chain polypropylene was not blended. The resulting polypropylene layer was of the coated type, as in Example 1. Although a thick film could be produced, the adhesion and surface metallization of the coated layer were insufficient. The tape test was not passed. Comparative Example 5

[0082] In Comparative Example 5, high-purity polypropylene (capacitor grade) was extruded. Maleic anhydride side-chain polypropylene was not blended, and the polypropylene layer was not coated. The optical properties of the resulting thin film were poor (haze value > 2), and the surface metallization had insufficient adhesion. Comparative Example 6

[0083] In Comparative Example 6, a three-layer multilayer polypropylene film was extruded. The first layer was made of materials tradenamed Moplen HP525J and Admer AT1179E. The second layer, which was in direct contact with the first layer, was polypropylene (Admer AT1179E), and the third layer was polypropylene (Moplen HP525J) from the prototype lot of the anti-adhesion film. The resulting film was coated with a polyurethane dispersion (as in Example 1). In the first test, film thicknesses below 18 μm could not be achieved. In the second test, a film thickness of 8 μm was achieved, but inappropriate process parameters and a very slow production rate prevented the production of thinner films.

[0084] As shown in the examples and comparative examples, the thin films of the present invention can be produced economically and have excellent properties (adhesion, friction and appearance, etc.), and can at least overcome the drawbacks of conventional thin films. [Explanation of symbols]

[0085] 100··Laminate material, 110··Polypropylene thin film, 112··Polypropylene layer, 114··Coating layer (polyurethane), 115··Nanoparticles, 116··Surface metallization layer, 120··Structural layer (e.g., paper substrate), 1000··Manufacturing method, 11001··Extrusion process, 1150··Stretching process (machine direction), 1200··Coating process, 1250··Stretching process (machine direction and / or cross direction), 1300··Surface treatment process, 1400··Surface metallization process, 1500··Lamination process,

Claims

1. A coated monolayer biaxially oriented polypropylene thin film (110) comprising a monolayer extruded polypropylene layer (112) made of an extruded polypropylene thin film and at least one coating layer (114), The extruded polypropylene layer (112) comprises homopolypropylene and maleic anhydride side chain polypropylene; A coated monolayer biaxially oriented polypropylene thin film (110) characterized in that the coating layer (114) is a dispersion coating layer containing polyurethane.

2. 2. The coated monolayer biaxially oriented polypropylene thin film (110) according to claim 1, wherein the coating layer (114) has a thickness in the range of 50 nm to 200 nm, 80 nm to 180 nm, or 100 nm to 150 nm.

3. 3. The coated monolayer biaxially oriented polypropylene thin film (110) according to claim 1 or 2, wherein the coating layer (114) comprises nanoparticles (115) having an average particle size in the range of 20 nm to 150 nm, 50 nm to 120 nm, or 80 nm to 100 nm.

4. 4. The coated monolayer biaxially oriented polypropylene thin film (110) according to claim 1, wherein the extruded polypropylene layer (112) is made of homopolypropylene and maleic anhydride side chain polypropylene.

5. The coated monolayer biaxially oriented polypropylene thin film (110) according to any one of claims 1 to 4, wherein the content of maleic anhydride side chain polypropylene in the extruded polypropylene layer (112) is at least 10% by weight, at least 15% by weight, or at least 20% by weight.

6. The polypropylene thin film (110) is 0.9 g / cm 3 ~0.95g / cm 3 , especially 0.91 g / cm 3 ~0.93g / cm 3 and / or The coated monolayer biaxially oriented polypropylene thin film (110) according to any one of claims 1 to 5, wherein the polypropylene thin film (110) has a thickness of 2 μm to 10 μm, 3 μm to 7 μm, or 4 μm to 6 μm.

7. 7. The coated monolayer biaxially oriented polypropylene film (110) of claim 6, wherein the polypropylene film (110) has a desired film thickness tolerance of ±0.4 μm, ±0.25 μm, or ±0.12 μm.

8. A coated monolayer biaxially oriented polypropylene film (110) according to any one of claims 1 to 7, wherein the coating layer (114) is based on an aqueous dispersion coating.

9. A metal coating layer (116) is formed on the coating layer (114); The coated monolayer biaxially oriented polypropylene thin film (110) according to any one of claims 1 to 8, wherein the metal coating layer (116) comprises aluminum, zinc, titanium, gold, silver, copper and / or chromium, as well as alloys and / or oxides thereof.

10. A cover layer (114) is formed on the first side of the polypropylene layer (112); 10. The coated monolayer biaxially oriented polypropylene film (110) according to any one of claims 1 to 9, wherein the second side of the polypropylene layer (112) opposite to the first side is uncoated and is subjected to a corona treatment and / or plasma surface treatment.

11. A laminate material, in particular a food packaging laminate (100), comprising at least one coated monolayer biaxially oriented polypropylene film (110) according to any one of claims 1 to 10 and a structural layer (120), A laminate (100) characterized in that a thin polypropylene film (110) is disposed on a structural layer (120).

12. 12. The laminate (100) of claim 11, wherein the structural layer (120) comprises or consists of a paper substrate.

13. 13. The laminate (100) according to claim 11 or 12, wherein the content of the polypropylene film (110) in the laminate (100) is at most 5% by weight, at most 4% by weight, or at most 3% by weight.

14. A method (1000) for producing a coated monolayer biaxially stretched polypropylene thin film (110) according to any one of claims 1 to 10, A step (1100) of extruding a polypropylene layer (112) comprising homopolypropylene and maleic anhydride side chain polypropylene; Directly coating (1200) the extruded polypropylene layer (112) with a coating layer (114) of an aqueous dispersion containing polyurethane; Stretching (1150; 1250) the polypropylene layer (112) in the machine direction and / or transverse direction; A method (1000) for producing a coated monolayer biaxially oriented polypropylene thin film (110), characterized in that a stretching step (1150; 1250) is carried out before and / or after the coating step (1200).

15. 15. The method (1000) of claim 14, wherein the production conveying speed for producing the coated biaxially oriented polypropylene film (110) is at least 300 m / min, at least 400 m / min, at least 500 m / min, at least 600 m / min, at least 700 m / min or at least 800 m / min, and the resulting polypropylene film (110) is formed into a biaxially oriented polypropylene film.

16. Guiding the extruded polypropylene layer (112) over a chill roll after the extrusion step (1100) and before the stretching step (1150); maintaining the chill roll at a temperature range of 35°C to 45°C or 38°C to 42°C; Optionally, guiding the extruded polypropylene layer (112) through a water bath at a temperature range of 20°C to 35°C or 22°C to 28°C.

17. machine direction stretching at a temperature in the range of 90°C to 120°C or 95°C to 112°C; and / or and performing machine direction stretching at a stretch ratio of 4 to 6 or 4.5 to 5.

18. and / or transverse stretching at a temperature in the range of 140°C to 190°C or 150°C to 185°C. and performing transverse stretching at a stretch ratio of 4 to 10, 5 to 9, or 6 to 9.

19. forming a coating layer (1200) on only one side of the polypropylene layer (112); and forming a surface treatment layer (1300) on the opposite side of the coating layer (1200), The method (1000) according to any one of claims 14 to 18, wherein the surface treatment layer is in particular a corona treatment layer and / or a plasma treatment layer.

20. forming a surface metallization (1400) on the coating layer (114) with a material comprising aluminum, zinc, titanium, gold, silver, silicon, copper, chromium, or alloys and / or oxides thereof to form a metal coating layer (116) on the coating layer (114); and / or 20. The method (1000) according to any one of claims 14 to 19, further comprising laminating a thin polypropylene film (110) onto a structural layer (120) having or consisting of a paper substrate.

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