Thin film manufacturing method and thin film manufacturing apparatus

Abstract

The present invention provides a method for producing a thin film containing a cycloolefin polymer component by a continuous stretching method and an apparatus for the same purpose. [Solution] The method for producing a thin film (A) includes the steps of: producing a thin film (A) comprising at least one layer containing at least 70% by weight of one or more types of semicrystalline alphaolefin polymers and 10% to 30% by weight of one or more types of cycloolefin polymers; and stretching the thin film (A) in the longitudinal direction using a longitudinal stretching apparatus having at least one pair of stretching rollers (40) that form a main stretching gap (S1) of at least 30 mm in width between at least one pair of stretching rollers (40).

Description

Technical Field

[0001] The present invention relates to a thin film manufacturing method and a thin film manufacturing apparatus.

Background Art

[0002] Biaxially stretched polypropylene (PP) films are commonly used in thin film capacitors. Techniques for improving the temperature resistance characteristics of polypropylene films using a mixture of polypropylene and cycloolefin polymer (COC) are known. However, cycloolefin polymers are extremely brittle polymers having a high glass transition temperature, and biaxial stretching of cycloolefin polymers may be difficult or impossible in some cases. Therefore, thin films made from polypropylene and cycloolefin polymers are extremely difficult to manufacture. For this reason, for example, only extremely thin films less than 5 μm, which are extremely expensive and have limited utility value, could be manufactured only by simultaneous stretching in the longitudinal and transverse directions.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, it is preferable to manufacture a thin film containing polypropylene and cycloolefin polymer by a continuous stretching method. Thus, an object of the present invention is to provide a method and an apparatus for the same purpose of manufacturing a thin film containing a cycloolefin polymer component by a continuous stretching method.

Means for Solving the Problems

[0004] The object of the present invention is achieved by a thin film manufacturing method. The thin film manufacturing method of the present invention includes at least the following steps. - A step of manufacturing a thin film having at least one layer containing at least 70% by weight of one or more semi-crystalline alpha-olefin polymers and 10% to 30% by weight of one or two or more cycloolefin polymers and - A step of forming a main stretching gap of at least 30 mm width between stretching rollers and stretching the thin film in the longitudinal direction by a longitudinal stretching device having at least a pair of stretching rollers.

[0005] The inventors have discovered that in a longitudinal stretching apparatus, expanding the main stretch gap by an amount greater than 30 mm, from the usual few mm, allows for the continuous stretching of brittle thin films made from a mixture of alpha-olefin polymers, such as a mixture of polypropylene and cycloolefin polymers. By expanding the main stretch gap by at least an order of magnitude, and expanding the entire main stretch gap longitudinally by an order of magnitude or more, the longitudinal stretching speed across the entire main stretch gap decreases, enabling slower longitudinal stretching and significantly increasing the stretching ratio in the longitudinal stretching apparatus.

[0006] In particular, the stretch gap dimension between two stretch rollers along the tangential of both stretch rollers corresponds to the tangent length between the contact points of multiple stretch rollers. Specifically, the thin film moves in the tangential direction. For example, one or more types of semicrystalline alpha-olefin polymers are one or more types of polypropylene.

[0007] In one embodiment of the present invention, the thin film comprises at least 75% by weight of one or more semicrystalline alpha-olefin polymers and 15% to 25% by weight of one or more cycloolefin polymers, particularly reliably achieving a high elongation ratio. The partial sum of the one or more alpha-olefin polymers and the one or more cycloolefin polymers is, for example, greater than 95% by weight, and particularly greater than 100% by weight. In this embodiment, the ratio of the one or more alpha-olefin polymers in the thin film can be set to 70% to 90% by weight.

[0008] Thin films can be constructed with a single layer, two layers, three layers, or four or more layers. More precisely, the single layer, multiple layers, or all constituent layers include one or more alpha-olefin polymers, particularly one or more types of polypropylene and one or more types of cycloolefin polymers, as described above. In one embodiment of the present invention, the longitudinal stretching apparatus forms a main stretching gap between a first pair of stretching rollers, and the auxiliary stretching gap is provided by a second pair of stretching rollers smaller than the main stretching gap. Between longitudinal stretching steps, the thin film is first stretched longitudinally along the main stretching gap, and then stretched longitudinally along the auxiliary stretching gap. Conversely, between longitudinal stretching steps, the thin film can also be stretched longitudinally first along the auxiliary stretching gap, and then stretched longitudinally along the main stretching gap. In this way, a high stretching ratio can be achieved.

[0009] In particular, to achieve a high elongation ratio, the dimensions of the main elongation gap are 50 mm or more, especially 100 mm or more. The dimensions of the auxiliary elongation gap are 4 mm or less, especially 2 mm or less, which allows for the extremely stable production of thin films.

[0010] In one embodiment of the present invention, the longitudinal stretching ratio along the main stretching gap is 3.4 or greater than 3.4, 3.6 or greater than 3.6, 4.0 or greater than 4.0, and in particular 4.5 or greater than 4.5, thereby enabling the production of an ultrathin film.

[0011] In one embodiment of the present invention, the longitudinal stretching ratio along the auxiliary stretching gap is 2 or less than 2, 1.5 or less than 1.5, and especially 1.2 or less than 1.2, so that the manufacturing method of the present invention can be stably carried out. For example, the total longitudinal stretching ratio is greater than 3.5, greater than 4.0, or especially 5.0 or greater than 5.0.

[0012] In one embodiment of the present invention, the thin film does not contain additives or anti-tack agents that reduce the tackiness of the thin film, and therefore can be given particularly good dielectric properties. The reason for reducing or preventing the tackiness of the thin film is, for example, to avoid adhesion problems of the thin film when winding the thin film onto or unwinding it from a winding device during other processes, where multiple thin film surfaces or other thin film surfaces come into contact with each other.

[0013] In any form, a thin film containing one or more anti-tack agents is considered to have reduced tackiness. Anti-tack agents reduce the tackiness of the thin film by reducing the tackiness of the thin film's surface or between the thin film and other surfaces. For example, solid spacers placed on the surface of a thin film are known to act as anti-tack agents.

[0014] The tackiness of the thin film produced by the manufacturing method of the present invention is prevented, for example, by a specific surface structure. In particular, the surface structure can be formed using the process temperature by controlling the target temperature with a cooling roller and a longitudinal stretching device. Due to the surface structure, an average surface finish (Ra / Rmax) can be performed, which prevents or reduces the tackiness of the thin film and facilitates subsequent processing steps of the thin film. Due to the specific surface structure or roughness, the use of an anti-tack agent is not required in this embodiment.

[0015] In one embodiment of the present invention, at least one, more than one, or all of the polypropylenes are semicrystalline polymers and / or homopolymers. For example, Borclean® (e.g., HC300BF, HC318BF) commercially available from Borealis, semicrystalline alpha-olefin polymers commercially available from The Polyolefins Ltd. (TPC) in Singapore, Korea Petrochemical Corporation (KPIC), or Prime Polymers can be used.

[0016] In one embodiment of the present invention, at least one, more, or all cycloolefin polymers are amorphous, have a glass transition temperature of 130°C to 180°C, and / or contain norbornene and ethylene as multiple monomers. The glass transition temperature is measured by differential scanning calorimetry based on the international standard ISO 11357 at a heating rate of 10 K / min.

[0017] For example, conformity certification types 6013S04, 6013M07, 6515S04, or 6017S04 from Topas Advanced Polymers, conformity certification types APL5014CL, APL5015CL, APL5016CL, or APL6015T from Mitsui Chemicals, Inc., conformity certification types Zenor1420R, Zenor1410R, Zeonex162R, Zeonex690R, or Zeonex790R from Zeon Corporation, conformity certification type ViViOn CBC from USI Corporation (located in Taiwan), and conformity certification type Arton from JSR Corporation can be used as cycloolefin polymers. Different mixed cycloolefin polymers disclosed in European Patent No. 4174120 can also be considered.

[0018] In one embodiment of the present invention, a longitudinal stretching apparatus is provided having a preheating region with a temperature higher than 110°C, particularly equal to or higher than 120°C and / or equal to or lower than 155°C, particularly equal to or lower than 145°C, and / or the longitudinal stretching apparatus has a stretching region with a temperature higher than 140°C, particularly equal to or higher than 150°C and / or equal to or lower than 165°C and particularly equal to or lower than 155°C. The above temperature, which is higher than the normal temperature for producing pure polypropylene thin films, is higher than the glass transition temperature of cycloolefin polymers, and an improved stretching process can be carried out.

[0019] For example, the corresponding region temperature is understood to be the temperature of the corresponding region roll. Furthermore, the cost-effectiveness can be further improved by transporting the thin film at a travel speed of 100 m / min to 400 m / min.

[0020] A manufacturing method according to one embodiment of the present invention further comprises the following steps: The process of transporting the thin film from the longitudinal stretching device to the transverse stretching device, A process for producing a laterally stretched thin film by stretching a thin film laterally using a lateral stretching apparatus, particularly having a width of 5 m to 13 m and / or a thickness of less than 5 μm, especially equal to or less than 4 μm.

[0021] For example, the film thickness of the thin film is equal to or greater than 2 μm, and in particular 3.8 μm. For example, the longitudinal thermal shrinkage of the thin film is a maximum of 5%, and in particular a maximum of 2.5%, measured according to the international standard ISO 11501 after 5 minutes of heating at 120°C, and the transverse thermal shrinkage is a maximum of 0.5%, and in particular a maximum of 0.05%.

[0022] In one embodiment of the present invention, the lateral stretching ratio of the lateral stretching apparatus is equal to or greater than 8, particularly equal to or greater than 8.5 and / or equal to or less than 10, particularly equal to or less than 9.5, and in particular the lateral stretching ratio by the lateral stretching apparatus is 9, and as a result a reliable manufacturing method with a high range of stretching ratios can be achieved. For example, the total stretching ratio is greater than 35, particularly greater than 40.

[0023] In one embodiment of the present invention, a heating furnace is provided to preheat the thin film before the transverse stretching process, and the temperature in the stretching region of the heating furnace is at least partially between 170°C and 175°C. This preheating allows the manufacturing process to be carried out more stably. The temperature inside the heating furnace used for preheating corresponds to the temperature in the stretching region of the heating furnace.

[0024] In particular, the thin film after lateral stretching has a final surface finish of 0.05 μm to 0.12 μm, especially 0.06 μm to 0.09 μm, which reliably prevents adhesion of the thin film. As a result, it can be determined as a lateral directivity measurement by tactile measurement using a Mahr measuring instrument.

[0025] A manufacturing method according to one embodiment of the present invention further includes the following steps: The step of removing the thin film from the cooling roller heated in the temperature range of 80°C to 100°C, particularly 90°C to 95°C, The step of conveying the thin film taken out from the cooling roller to the longitudinal stretching device.

[0026] The manufacturing method of the embodiment additionally includes at least one of the following steps to perform further processing on the thin film: The step of activating the surface of the thin film by corona treatment means, The step of winding up the thin film. The additional steps are carried out after the longitudinal and / or transverse stretching steps. Corona treatment can be applied to one or both sides of the thin film. Additional steps, particularly offline, can apply metallization surface treatment to one or both sides of the sufficiently stretched thin film.

[0027] Metallization surface treatment can be carried out on one or both sides of the thin film surface. In particular, metallization surface treatment made of metal or metal alloy can be carried out. Furthermore, by metal surface treatment in a single layer or multiple layers, a plurality of different layers with different compositions can be formed on the thin film. In one embodiment of the present invention, the metallization treatment layer includes aluminum, zinc, gold, silver, magnesium or a suitable alloy of the above materials. The metallization treatment film thickness can be formed, for example, in the range of 10 nm to 100 nm. Also, the metallization treatment layer can be assembled.

[0028] In particular, the metallization surface-treated thin film can be used as a capacitor thin film according to its structure. At least one electrode of the capacitor can be formed by metallization treatment or a metallization treatment surface can be provided. Also, a thin film manufacturing system using a longitudinal stretching device, particularly the entire device set for implementing the above method, can achieve this purpose. The features and advantages related to the manufacturing method of the present invention can apply the same features and advantages as the manufacturing device of the present invention. Conversely, the features and advantages related to the manufacturing device of the present invention can be applied to the manufacturing method of the present invention.

[0029] The manufacturing device of the present invention includes, for example, an extrusion device, a casting device, a transverse stretching device (TDO, transverse orienter), a processing device (for example, a corona treatment device) and / or a winding device.

Brief Description of the Drawings

[0030] Other features and advantages of the present invention will become apparent from the accompanying drawings and the description below. The accompanying drawings are shown below. [Figure 1] Perspective view of a thin film manufacturing apparatus according to an embodiment of the present invention. [Figure 2] Cross-sectional view of the longitudinal stretching device used in the thin film manufacturing apparatus shown in Figure 1. [Figure 3] Schematic diagram showing the extension structure of the longitudinal extension device shown in Figure 2. [Figure 4] Flowchart of a method for manufacturing a thin film according to an embodiment of the present invention. [Figure 5] Elongation rate diagram shown as a width function of the elongation gap [Modes for carrying out the invention]

[0031] Figure 1 shows a perspective view of a thin film A manufacturing apparatus 10 comprising various different devices and parts. The thin film manufacturing apparatus 10 is, for example, a thin film manufacturing apparatus for capacitor thin films, but the accompanying drawings are merely an example of one embodiment of the present invention and do not reduce the scope of protection of the present invention.

[0032] In the illustrated example, the thin film manufacturing apparatus 10 comprises an extruder 12, a casting apparatus 14, at least one longitudinal stretching apparatus 16 (MDO, "machine direction orientation apparatus"), a transverse stretching apparatus 18 (TDO, "transverse orientation apparatus"), a processing apparatus 20, and a winding apparatus 24. The extruder 12 is an extruder that provides molten resin as at least one starting material (product) to be formed in the casting apparatus 14 and supplied from the casting apparatus 14 to a cooling roller, which will be the material for forming the final thin film A.

[0033] The thin film produced by the thin film manufacturing apparatus 10 has one layer or multiple layers. To produce a multi-layered thin film, multiple layers or all layers can be formed using a single extruder, or a single layer can be formed using a single extruder. For example, the single or multiple extruders are single-screw extruders, cascade extruders, and / or twin-screw extruders. Other mixing and processing equipment such as a kneader or a planetary roller extruder can also be used.

[0034] The cooling rollers housed in the casting apparatus 14 are temperature-controlled. For example, the transverse stretching apparatus 18 disclosed in German Patent Application Publication No. 102021128332 has a heating furnace 25 with various regions for controlling the temperature of the thin film along the normal direction of movement of the thin film manufacturing apparatus 10 or the opposite direction. The transverse stretching apparatus 18 includes a drive for the thin film A, which has two transport rails for transporting the thin film through the various regions. Multiple gripping devices are guided along each transport rail in a known structure.

[0035] The gripping device grips the thin film A and moves it along the transport rail by an appropriate drive device, so the thin film A is transported by the lateral stretching device 18. In the first region called the preheating region, the thin film is heated. In the subsequent second region ("stretching region"), the thin film is stretched laterally, so the width and thickness of the thin film at the end of the second region are greater than the width and thinner than the thickness of the thin film at the beginning of the second region. In the lateral stretching region, the spacing between the rails of the drive device increases along the transport direction of the thin film, so the width of the thin film is stretched wider and the thickness of the thin film decreases.

[0036] In the third region ("heat treatment region") and the fourth and subsequent regions ("post-heating region" and / or "annealing region"), the thin film is exposed to high temperatures, for example, to reduce or eliminate internal stress in the thin film. The thin film is cooled in the final region ("cooling region"). Further regions, called neutral regions, perform the operations of different regions. For example, the neutral region does not provide ventilation. Neutral regions are placed between multiple such regions, for example, between the annealing region and the cooling region. The transverse stretching apparatus 18 is disclosed, for example, in International Publication No. 2014 / 094803.

[0037] The area of ​​the lateral stretching device 18 is divided into different forms and / or designed with different length conditions. For example, fewer or shorter neutral areas may be provided, or additional neutral areas may be placed at other locations. Modifications to the remaining area may also be considered.

[0038] The processing apparatus 20 is a device for modifying the surface of a thin film, for example, by corona treatment, to establish good metal adhesion. Corona treatment can be applied to one or both sides of the thin film. The thin film A to be formed can be wound up using the winding device 24, which is the final device for the thin film A in the tensile direction. The winding device 24 has a winding core for winding the thin film A.

[0039] Figure 2 is a cross-sectional view of the longitudinal stretching apparatus 16. The longitudinal stretching apparatus 16 comprises a supply area 26, a preheating area 28, a longitudinal stretching area 30, a heat treatment area 32, and a discharge area 34. The supply area 26 is provided with at least one movable roller 36 that guides the thin film A to the preheating area 28. The movable roller 36 sets the tension of the thin film.

[0040] The preheating region 28 has a plurality of preheating rollers 38. The surfaces of the preheating rollers 38 are, for example, ceramic coated, chrome plated, or Teflon® coated. In the illustrated embodiment, a chrome plated preheating roller 38 is used at the entrance of the preheating region 28, and further Teflon® coated preheating rollers 38 are used along the direction of transport of the thin film. The other rollers are similarly controlled in which the surfaces of the preheating rollers 38 are heated to a specific temperature as the thin film A leaves the last preheating roller 38. This temperature of the thin film A is referred to herein as the temperature of the preheating region 28.

[0041] In the longitudinal stretching region 30 shown in Figure 3, which is provided adjacent to the preheating region 28 in the direction of movement (drawing) of the thin film A, at least one pair of stretching rollers 40 are arranged. In the illustrated example, the longitudinal stretching apparatus 16 has four stretching rollers 40 in the longitudinal stretching region 30 which forms two pairs of stretching rollers 40. In addition, multiple guide rollers 42 and pressure rollers 44 are provided in the longitudinal stretching region 30.

[0042] In the illustrated embodiment of the present invention, guide rollers 42, respectively, provided at the front and rear of two pairs of stretch rollers 40 in the direction of movement of the thin film A, receive the thin film A from the preheating region 28 and supply the thin film A to the heat treatment region 32. Figure 3 schematically shows the longitudinal stretching region 30, i.e., the stretching apparatus, where the stretch rollers 40 are provided. As shown in the figure, one pressure roller 44, assigned to each of the two pairs of stretch rollers 40 in the drawing direction, applies pressure to the thin film A against the stretch rollers 40 assigned in a known manner.

[0043] The trailing rollers 40 of each pair of stretch rollers 40 are separated by a certain distance from the leading stretch roller 40 of each pair. A stretch gap is formed between the two stretch rollers 40 of each pair. A main stretch gap S1 is formed between the first pair of stretch rollers, i.e., the pair of stretch rollers 40 that precede in the pulling direction, and an auxiliary stretch gap S2 is formed between the second pair, i.e., the trailing pair of stretch rollers 40.

[0044] The dimensions of the stretch gaps S1 and S2 can be determined as follows. In the side view or cross-section, a tangent T is obtained along the thin film A along the stretch gaps S1 and S2. The tangent T is a common tangent that simultaneously contacts the corresponding pair of stretch rollers 40 and has contact points P with each stretch roller 40. The length of the tangent T between the two contact points P is the length of the corresponding stretch gap. The main stretch gap S1 is at least 30 mm, especially 50 mm or more, when converted to dimension G1. Dimensions G1 of 100 mm or more than 100 mm are also possible. The auxiliary stretch gap S2 is 4 mm or less than 4 mm, especially 2 mm or less, when converted to dimension G2.

[0045] The thin film A is stretched through the main stretching gap S1 in the longitudinal direction, and the rear ends of the two stretching rollers 40 constituting the first stretching roller pair rotate at high speed, so that the first stretching step of the thin film A is carried out in the main stretching gap S1. In the first stretching step, the thin film A becomes longer and thinner, forming substantially the final thin film A. In the auxiliary stretching gap S2, the thin film A is stretched again in the longitudinal direction, becoming even thinner and longer.

[0046] The temperature of the longitudinal stretching region 30 can be controlled in accordance with the temperature of the thin film. Similar to the preheating region 28, a plurality of heating rollers 46, which are ceramic-coated, chrome-plated, or Teflon®-coated to control surface temperature resistance, are provided in the heat treatment region. The internal stress of the formed thin film A is relieved or removed and / or tempered (annealed) in the kneading region 32. The thin film manufacturing apparatus 10 is configured to carry out the above manufacturing method of thin film A.

[0047] The method for producing a thin film A having a single layer is as follows. The thin film produced by the production method of the present invention can be a thin film with at least one layer, or a thin film having multiple identical or different layers. The starting material of the extruder 12 contains at least 70% by weight of a semicrystalline alpha-olefin polymer, particularly polypropylene, and 10% to 30% by weight of a cycloolefin polymer.

[0048] Blends of multiple polypropylenes totaling 70% by weight or more than 70% by weight are also possible. One, multiple, or all polypropylenes are semicrystalline polymers and / or homopolymers. Available commercially available polypropylenes include, for example, Borealis' Borclean® (e.g., HC300BF, HC318BF), The Polyolefins Ltd. (TPC) in Singapore, Korea Petrochemical Corporation (KPIC), or Prime Polymer Ltd., which are semicrystalline alphaolefin polymers or similar polymers.

[0049] Furthermore, single-type, multiple-type, or all-type cycloolefin polymers are amorphous and have a glass transition temperature of 130°C to 180°C. Multiple-type cycloolefin polymers can also be blended with starting materials containing norbornene and / or ethylene as monomers. The total blending amount of cycloolefin polymers is 10% to 30% by weight. The glass transition temperature is measured according to ISO 11357 standards at a heating rate of 10 K / min.

[0050] The cycloolefin polymers that can be used include 6013S04, 6013M07, 6015S04, or 6017S04 from Topas Advanced Polymers, APL5014CL, APL5015AL, APL5016SL, or APL6015 from Mitsui Chemicals, Inc., Zenor 1401R, Zeonex 162R, or Zeonex 790R from Zeon Corporation, ViViOn CBC from USI Corporation in Taiwan, or Arton from JSR Corporation. In particular, heterogeneous cycloolefin polymers to be blended are disclosed in European Patent No. 4174120.

[0051] For example, a single or multiple cycloolefin polymer and a single or multiple polypropylene constitute a starting material in an amount of 95% by weight or more than 95% by weight, and especially 100% by weight. A starting material can be considered that includes at least 75% by weight of a single or multiple polypropylene and 15% to 25% by weight of a single or multiple cycloolefin polymer.

[0052] The starting material does not contain additives that are typically used to reduce the tackiness of the thin film. Therefore, it does not contain solid materials that form the surface roughness of the thin film. The starting material prepared in the main stretching gap S1 is supplied to the extruder 12 (Step S1, Figure 4). The starting material can be composed of a composite (compound) obtained by mixing one or more types of alpha-olefin polymers with one or more types of cycloolefin polymers in an equivalent mixing ratio. The composite can be used as granules itself.

[0053] The starting material may be a pre-mixed composite material or a granular mixture of each component. When filling the extruder 12 with the starting material, the operator can mix various granular materials from a supply device, for example, as the mixed material or starting material for the thin film manufacturing apparatus 10. Next, the starting material is melted in the extruder 12 and extruded as a molten material onto the cooling roller of the casting apparatus 14 (step S2 in Figure 4). The cooling roller is heated to a temperature range of 80°C to 100°C, particularly 90°C to 95°C.

[0054] The surface roughness of the thin film A to be formed is controlled by temperature control of the cooling roller. The temperature range generates an average surface finish Ra of the thin film A that has been transversely stretched to a thickness of 0.05 μm to 0.12 μm, and especially 0.06 μm to 0.09 μm (Figure 4, step S3). The thin film A is transported from the casting apparatus 14 to the longitudinal stretching apparatus 16 in the region of step S4.

[0055] In the longitudinal stretching apparatus 16, the thin film A is first transported through a preheating region 28 at a temperature of 110°C or above 110°C, particularly 120°C or above 120°C, but below 155°C, particularly 145°C or below 145°C. Therefore, the thin film A passing through the preheating region 28 has a temperature of 110°C or above 110°C, particularly 120°C or above 120°C, but below 155°C, particularly below 145°C. Thus, the thin film A is preheated (step S5).

[0056] The temperature of the longitudinal stretching region 30 set for thin film A is greater than 140°C, particularly greater than 150°C, 165°C, or greater than 165°C, particularly greater than 155°C, or less than 155°C. This is to select the roll temperature and maintain thin film A at a predetermined temperature. Subsequently, thin film A is stretched in the longitudinal direction, i.e., in the tension or transport direction (step S6). The main stretching gap S1 is set to a dimension of at least 30 mm, particularly 50 mm or greater than 50 mm, 100 mm or greater than 100 mm.

[0057] Since the length G2 of the auxiliary stretching gap S2 is 4 mm or less than 4 mm, and especially 2 mm or less than 2 mm, the main stretching gap S1 is at least orders of magnitude smaller. The thin film A is first guided through the main stretching gap S1, and then guided through the auxiliary stretching gap S2 and stretched. However, it is also possible to first perform a first stretch along the auxiliary stretching gap S2, i.e., the small stretching gap, and then perform a second stretch along the main stretching gap S1, i.e., the large stretching gap.

[0058] When increasing the rotational speed of the subsequent stretching roller 40 in the main stretching gap S1, the rotational speed of the stretching rolls 40 of the first stretching roll pair is selected such that the stretching ratio along the main stretching gap S1 is equal to or greater than 3.4, and especially greater than 3.6. Stretching ratios equal to or greater than 4.0, and especially greater than 4.5, can also be considered. Larger stretching ratios, particularly those for larger dimensions G1 in the main stretching gap S1, can also be selected.

[0059] After stretching along the main stretching gap S1, the thin film A is further stretched and thinned in the longitudinal direction. Subsequently, when stretching the thin film A along the auxiliary stretching gap S2, the rotational speed of the stretching rollers 40 of the second stretching roller pair is selected so that the longitudinal stretching ratio along the auxiliary stretching gap S2 is equal to or less than 2, in particular equal to or less than 1.5, and even more specifically equal to or less than 1.2.

[0060] For example, the rotational speed of the leading stretching roller 40 of the second pair of stretching rollers 40 corresponds to the rotational speed of the trailing stretching roller 40 of the first pair of stretching rollers 40. The rotational speed of the trailing stretching roller 40 of the second pair of stretching rollers 40 is greater than that of the corresponding first stretching roller 40 of the second pair, and determines the manufacturing speed of the thin film A or the manufacturing speed of the thin film manufacturing apparatus 10.

[0061] The drive speed, determined by the rotational speed of the subsequent stretch rollers 40 following the second pair of stretch rollers 40, is, for example, 100 m / min to 400 m / min. The total longitudinal stretch ratio MDx through the main stretch gap S1 and the auxiliary stretch gap S2 is, for example, greater than 3.5 or greater than 4.0, and especially equal to or greater than 5.0.

[0062] High stretch ratios (MDx) of inherently fragile thin films made from polypropylene and cycloolefin polymers can be produced by a significantly increased main stretch gap S1, as shown in Table 1 and Figure 5 below.

[0063] [Table 1]

[0064] Table 1 shows the stretching test results for four different thin film specimens with different dimensions G1 of the main stretching gap S1. In each stretching test, the longitudinal stretching ratio MDx gradually increased from 3.5 at the start, while subsequent transverse stretching yielded a constant stretching ratio TDx = 9.

[0065] The last column indicates flawless thin films with (+) and damaged thin films due to insufficient stretching, such as cracks, with (-). The highest value of the stretch ratio MDx indicates the maximum stretch ratio. Thin film A was stretched to the maximum stretch ratio.

[0066] In the stretching test, starting with a main stretching gap S1 of 30 mm (dimension G1), the stretching ratio was increased beyond 3.5 to the maximum longitudinal stretching ratio MDx. Furthermore, by further increasing the dimension G1 of the main stretching gap S1, a further increase in the longitudinal stretching ratio MDx was achieved.

[0067] As shown in Figure 5, the expanding main stretch gap S1 results in a decreasing stretching rate (henki rate) of the thin film A through the main stretch gap S1, thus increasing the longitudinal stretching ratio MDx. Figure 5 shows the stretching rate D as a function of the dimension G1 of the main stretch gap S1. The lower the stretching rate, the stronger the stretching (MDx > 3.5) that can be performed even on a fragile thin film.

[0068] A longitudinal stretching apparatus 16 can also be considered, which has more stretching roller pairs than the two stretching rollers 40 and has multiple additional auxiliary stretching gaps. After longitudinal stretching, the thin film is transported from the longitudinal stretching apparatus 16 to the transverse stretching apparatus 18 (step S7 in Figure 4).

[0069] In the lateral conveying device 18, the thin film is stretched in the lateral direction (Step S8, Figure 4). The lateral stretching ratio of the lateral stretching device 18 is equal to or greater than 8, in particular equal to or greater than 8.5 and / or less than 10, in particular equal to or less than 9.5. For example, the lateral stretching ratio is 9.

[0070] The regional stretching ratio, i.e., the stretching ratio in the longitudinal and transverse directions, exceeds 35, and particularly exceeds 40. The film thickness of thin film A after transverse stretching is, for example, less than 5 μm, particularly less than 4 μm. At the same time, the thin film can be formed to a film thickness equal to or greater than 2 μm.

[0071] For example, a thin film A can be formed to a thickness of 3.8 μm after the transverse stretching process. The width of thin film A after the transverse stretching process is 5 m to 13 m. During the transverse stretching process, the heating furnace 25 in the stretching region can be maintained at a temperature of 170°C to 175°C.

[0072] Thin film A is transported from the transverse stretching device 18 to the processing device 20. The processing device 20 performs corona treatment (step S9) on one or both sides of thin film A. After that, thin film A is wound up by the winding device 24 (step S10).

[0073] Thus, a thin film A comprising at least one type of 70% by weight polypropylene and at least one or more types of cycloolefin polymers in amounts from 10% to 30% by weight is produced by a continuous stretching process that includes a longitudinal stretching step and a transverse stretching step.

[0074] [Table 2]

[0075] Table 2 shows four examples of product thin films, with Examples 2 and 3 in Table 2 being thin films manufactured according to the present invention. The total thin film contains 80% by weight of polypropylene (PP) and 20% by weight of cycloolefin polymer (COC). The glass transition temperature (Tg) of the cycloolefin polymer and the type of stretching process (continuous or simultaneous) are indicated by the type of stretching process. The longitudinal stretching ratio (MDx), the achieved regional stretching ratio (ASR), and the manufactured thin film thickness (t) are also shown in Table 2.

[0076] In Examples 1, 2, and 3, a sequential stretching process was selected in which a longitudinal stretching process and a transverse stretching process were performed individually and at different times using two different manufacturing devices on the same production line. Example 4 is a comparative example in which a thin film was stretched simultaneously in the longitudinal and transverse directions using a simultaneous stretching device.

[0077] The dimensions G1 of the main stretching gap S1 are shown in Examples 1, 2, and 3, and the dimensions G2 of the auxiliary stretching gap S2 were 1 mm to 2 mm. There were no changes to the other parameters used in thin film production in Examples 1, 2, and 3. The temperature of the cooling roller in the preheating area 28 of the longitudinal stretching apparatus 16 was 95°C, and the temperature of the stretching area in the heating furnace 25 of the transverse stretching apparatus 18 was 170°C to 175°C.

[0078] The thin film of Example 4 was fabricated with a longitudinal stretch ratio of 5.5. It is clear that the longitudinal stretch ratio MDx is due to the significant high regional stretch ratio ASR. The high regional stretch ratios used in Examples 2 and 3 also improve the characteristics of thin film A, such as the breakdown voltage BDV shown in Table 3 below.

[0079] [Table 3]

[0080] Table 3 shows the thin film properties obtained for Examples 1 to 4, including mean surface roughness (Ra), maximum surface roughness (Rmax), longitudinal shrinkage rate (MD), transverse shrinkage rate (TD), and yield voltage (BDV). When measured at 120°C for 5 minutes according to ISO 11501 standards, the thin films of Examples 1 to 4 showed a maximum longitudinal thermal shrinkage rate of 5%, particularly a maximum of 2.5%, and a maximum transverse thermal shrinkage rate of 0.5%, particularly a maximum of 0.05%.

[0081] It is clear that thin films with a thickness of less than 4 μm can be produced by the continuous biaxial stretching method using the manufacturing method of the present invention. At the same time, Tables 2 and 3 show that the regional stretching ratio and physical properties of the thin films produced by the present invention (Examples 2 and 3), particularly the low surface roughness and high yield voltage, approach the properties of the thin film produced by simultaneous stretching (Example 4). Simultaneously stretched thin films are considered to be a quality standard.

[0082] The thin film manufacturing apparatus that sequentially stretches and sequentially stretches thin films is also extremely inexpensive, and since the purchase and maintenance costs are lower than those of simultaneous stretching apparatus, there is an advantage in that thin films with the quality of simultaneously stretched thin films using the manufacturing method of the present invention can be manufactured at low cost. Examples 2 and 3 can be manufactured with extremely stable operation, as thin film lengths exceeding 30,000 m are possible.

[0083] High breakdown voltage thin films manufactured using the manufacturing method of the present invention can be used as dielectrics for capacitors. These types of capacitors typically meet the high-quality requirements of the automotive and electric transportation sectors. Furthermore, the gist of the present invention is that thin films manufactured by the present invention, particularly thin films with metal coating on one or both sides, can be used as dielectrics for manufacturing capacitors.

Claims

1. - A step of producing a thin film (A) comprising at least one layer containing at least 70% by weight of one or more types of semicrystalline alphaolefin polymers and 10% to 30% by weight of one or more types of cycloolefin polymers, - A main stretch gap (S) of at least 30 mm in width between at least one pair of stretch rollers (40) 1 A step of stretching a thin film (A) in the longitudinal direction using a longitudinal stretching apparatus (16) having at least one pair of stretching rollers (40) that form a thin film (A), A method for producing a thin film (A) characterized by containing the following.

2. A method for producing a thin film (A) according to claim 1, wherein the thin film (A) comprises at least 75% by weight of one or more semicrystalline alphaolefin polymers and 15% to 25% by weight of one or more cycloolefin polymers.

3. The longitudinal stretching device (16) comprises a plurality of stretching rollers (40) that constitute a second pair, A second pair of multiple stretch rollers (40) with an auxiliary stretch gap (S 2 ) is formed, Auxiliary stretching gap (S 2 ) is the main extension gap (S 1 Smaller than ) During the longitudinal stretching process, the main stretching gap (S 1 The process involves stretching a thin film (A) in the longitudinal direction along the ) and then the auxiliary stretching gap (S 2 A process of stretching a thin film (A) in the longitudinal direction along ) or a process of adding an auxiliary stretching gap (S) between longitudinal stretching steps. 2 The process involves stretching a thin film (A) in the longitudinal direction along the main stretch gap (S 1 A method for producing a thin film (A) according to claim 1, comprising the step of stretching the thin film (A) in the longitudinal direction along the ).

4. The main stretching gap (S 1 ) has a dimension of 50 mm or more than 50 mm or 100 mm or more than 100 mm and / or the auxiliary stretching gap (S 2 ) has a dimension of 4 mm or less than 4 mm or 2 mm or less than 2 mm. The method for manufacturing the thin film (A) according to claim 1.

5. Main drawing gap (S 1 The longitudinal elongation ratio along ) is equal to or greater than 3.4, equal to or greater than 3.6, equal to or greater than 4.0, or equal to or greater than 4.

5. Auxiliary stretching gap (S 2 A method for producing a thin film (A) according to claim 1, wherein the longitudinal stretching ratio along the ) is equal to or greater than 2, equal to or less than 1.5, or equal to or less than 1.

2.

6. The thin film (A) is a method for producing the thin film (A) according to claim 1, which does not contain additives.

7. A method for producing a thin film (A) according to claim 1, wherein at least one, more than, or all of the polypropylenes are semicrystalline polymers and / or homopolymers.

8. A method for producing a thin film (A) according to claim 1, wherein at least one, more than, or all of the cycloolefin polymers are amorphous and have a glass transition temperature between 130°C and 180°C and / or contain norbornene and ethylene as monomers.

9. The longitudinal stretching apparatus (16) is equipped with a preheating area (28) where the temperature is equal to or greater than 110°C, equal to or greater than 120°C, equal to or less than 150°C, or equal to or less than 145°C and / or A method for producing a thin film (A) according to claim 1, wherein the longitudinal stretching apparatus (16) comprises a stretching region (30) with a temperature equal to or exceeding 140°C, equal to or exceeding 150°C and / or equal to or exceeding 165°C, or equal to or less than 155°C.

10. A method for manufacturing a thin film (A) according to claim 1, comprising the step of transporting the thin film (A) at a speed between 100 m / min and 400 m / min after it has passed through a longitudinal stretching device (16).

11. A process of transporting the thin film (A) from the longitudinal stretching device (16) to the transverse stretching device (18), A method for producing a thin film (A) according to claim 1, comprising the step of stretching the thin film (A) in the transverse direction using a transverse stretching device (18).

12. A method for producing a thin film (A) according to claim 11, wherein the thin film (A) that has undergone a transverse stretching process has a width of 5 m to 13 m and / or a film thickness of 5 μm or less than 5 μm or 4 μm or less than 4 μm.

13. The lateral stretching ratio of the lateral stretching device (18) is 8 or greater than 8, or 8.5 or greater than 8.5, 10 or less than 10, or 9.5 or less than 9.

5. The method for manufacturing a thin film (A) according to claim 11, wherein the transverse stretching ratio of the transverse stretching apparatus (18) is 9.

14. The method for producing a thin film (A) according to claim 11, wherein the transverse stretching apparatus (18) is equipped with a heating furnace for preheating the thin film (A) before the transverse stretching process.

15. The method for producing a thin film (A) according to claim 14, wherein the temperature of the heating furnace is at least a part of 170°C to 175°C.

16. A method for producing a thin film (A) according to claim 1, wherein the thin film (A) has an average surface finish of 0.05 μm to 0.12 μm or 0.06 μm to 0.09 μm.

17. The process involves extruding a thin film (A) onto a cooling roll, A method for producing a thin film (A) according to claim 1, comprising the step of transporting the thin film (A) from a cooling roll to a longitudinal stretching device (16).

18. A method for producing a thin film (A) according to claim 17, comprising the step of heating a cooling roll to a temperature range of 80°C to 100°C or 90°C to 95°C.

19. A process of modifying the surface of a thin film (A) by corona treatment, A method for producing a thin film (A) according to claim 1, comprising the step of winding up the thin film (A).

20. In a thin film (A) manufacturing apparatus (10) equipped with a longitudinal stretching device (16), A thin film (A) manufacturing apparatus (10) characterized by carrying out the thin film (A) manufacturing method described in any one of claims 1 to 19 using a longitudinal stretching apparatus (16) and / or a manufacturing apparatus (10).

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