Microporous film manufacturing apparatus, suction roll, and microporous film manufacturing method

Abstract

To provide a manufacturing apparatus and a manufacturing method of a microporous film by which a wrinkle and breakage can be prevented and the film can be manufactured with high productivity.SOLUTION: A manufacturing apparatus of a microporous film F includes a cutting process 10 in which an ear part F2 is separated from the long microporous film F and the microporous film F as a product part F1 can be obtained. In the cutting process 10, a cutting device 20, at least one drive roll 12, at least one suction roll 42, and a product part conveying roll 13 are arranged in this order from a most upstream side. The suction roll 42 includes many suction holes which have a shape for improving suction effect, are caused to communicate with a negative pressure source, and are opened on a metal roll surface. The suction hole forms a groove shape continuing over a range exceeding a film width in a roll width direction, and has a groove shape continuing in a roll circumference direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for producing a long microporous film, a suction roll, and a method for producing a microporous film. [Background technology]

[0002] Polyolefin microporous films are widely used as separation membranes, separators, etc. for the separation and selective filtration of various substances. For example, polyolefin microporous films are used as microfiltration membranes, fuel cell separators, capacitor separators, etc. Among these, polyolefin microporous films are particularly suitable for use as separators for lithium ion batteries, which are widely used in notebook personal computers, mobile phones, digital cameras, etc. This is due to the excellent membrane mechanical strength and shutdown properties of polyolefin microporous films.

[0003] For example, Patent Document 1 describes a method for producing a polyethylene microporous film, in which a mixture containing a film-forming diluent is subjected to a first stretching, and the microporous film from which the film-forming diluent has been removed is subjected to a second stretching.

[0004] The microporous film from which the diluent has been extracted after the second stretching has uneven thickness of both edges in the width direction and shape of the end faces, so it is fed, for example, between a cutting device having circular upper and lower blades, and both edges are cut off in the conveying direction.

[0005] For example, Patent Document 2 describes a method for manufacturing a fragile film in which the film after being cut by the cutting device passes through a conveying roll (free roll) and a single suction roll, and then the product portion and the edge portion are wound up separately by a winding roll.

[0006] Patent document 3 describes a trimming device in which the thermoplastic resin film after being cut by the cutting device passes through two S-nip mechanism conveying rolls located at the most upstream side, and the product portion and the edge portion are sent separately downstream.

[0007] Furthermore, Patent Document 4 describes that in a method for producing a microporous film, the microporous film is prone to tearing and the pores are easily crushed, and therefore must be transported under lower tension than a general resin film without pores.

[0008] Patent Document 5 describes a suction roll having slits that are continuous with suction holes over a range not exceeding the film width in the roll width direction. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-63547 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-182844 [Patent Document 3] Japanese Patent Application Publication No. 63-77697 [Patent Document 4] Republished Publication No. 2013-10062 [Patent Document 5] Japanese Patent Application Publication No. 8-133536 Summary of the Invention [Problem to be solved by the invention]

[0010] However, when a conventional technique (Patent Document 2) in which the edge portions are cut and then passed through a suction roll to wind up the product portion and edge portions separately on a take-up roll is applied to a microporous film, if a difference occurs between the conveying tension of the product portion and the conveying tension of the edge portions, even if the tension difference ΔT is 5 N / m or less, it propagates to the cutting portion (the position where the cutting device is located in the cutting process), causing the film to tear, resulting in a problem of reduced production efficiency. This is because the air-permeable microporous film has lower adsorption on the suction roll compared to general non-porous resin films.

[0011] Furthermore, as described in Patent Document 2, when a conveying roll (free roll) was installed between the cutting section and the suction roll and applied to a microporous film, if a difference occurred between the conveying tension of the product section and the conveying tension of the selvage section, the propagation of the tension difference to the cutting section was suppressed, but the tension loss due to the free roll made it impossible to properly adjust the tension, causing wrinkles on the suction roll and possibly tearing the film, resulting in a decrease in production efficiency. This is because, in the case of a microporous film that needs to be conveyed under the low tension, the impact of tension loss on the conveying tension is significant.

[0012] As described in Patent Document 3, when the conventional technology of separating the product part and the selvage part after cutting the selvage part and passing it through two rolls (S-nip mechanism) was applied to a microporous film, if a difference occurred between the conveying tension of the product part and the conveying tension of the selvage part, the tension difference could not be prevented from propagating to the cutting part, and the film may tear, resulting in a problem of reduced manufacturing efficiency.

[0013] As described in Patent Document 5, when the conventional technology of a suction roll structure having suction holes and slits (hereinafter referred to as grooves) in a range not exceeding the film width in the roll width direction was applied to a microporous film, the edge portions at both ends of the film did not have suction holes or grooves, so if a difference in conveying tension occurs between the product portion and the edge portions, the tension difference cannot be prevented from propagating to the cutting portion, which can cause the film to tear and reduce manufacturing efficiency.

[0014] The present invention has been made in view of the above points, and aims to provide a microporous film manufacturing apparatus and method that can produce a microporous film with high productivity by preventing wrinkles and tears. [Means for solving the problem]

[0015] A microporous film manufacturing apparatus for cutting an elongated microporous film substrate along a traveling direction of the microporous film substrate into edge portions at both ends and a microporous film that is a product portion in the center, to obtain the product portions from the microporous film substrate, comprising: a cutting device that cuts the edge portion and the product portion of the microporous film substrate; At least one substrate conveying roll and at least one suction roll that simultaneously convey the cut product portion and the edge portion; a product portion conveying roll that conveys the cut product portion separately from the edge portion; and an edge transport roll that transports the edge portion after cutting separately from the product portion, the substrate transport roll is a drive roll, The microporous film manufacturing apparatus, wherein the cutting device, the substrate conveying roll, the suction roll, and the product section conveying roll are arranged in this order from the most upstream side to the downstream side in the conveying direction of the microporous film substrate.

[0016] According to the microporous film manufacturing apparatus of the present invention, after the edge portions are cut, the product portion and the edge portions are simultaneously conveyed through the drive roll and the suction roll in that order, thereby suppressing the propagation of the tension difference between the product portion and the edge portions at the cutting section, preventing film breakage and improving manufacturing efficiency. In addition, since appropriate tension adjustment is possible, the occurrence of wrinkles on the suction roll can be suppressed, improving manufacturing efficiency.

[0017] 2. The microporous film manufacturing apparatus according to claim 1, further comprising a stretching device that is provided upstream of the cutting device in the conveying direction of the microporous film substrate, and that grips both ends of the long microporous film substrate in the width direction and stretches the microporous film using the grippers.

[0018] By stretching the microporous film in the width direction (direction perpendicular to the film conveying direction) using grippers at both ends before the cutting device, the thickness in the width direction can be made uniform, and film tearing due to uneven thickness at the cutting section can be suppressed, thereby improving manufacturing efficiency.

[0019] The suction roll has suction holes formed at a number of locations on the surface of the suction roll in the longitudinal direction and the circumferential direction, the suction holes being connected to a negative pressure source; transverse grooves formed on the surface of the suction roll to connect the suction areas of the suction holes arranged along the length of the suction roll to improve the suction effect; and longitudinal grooves formed on the surface of the suction roll to connect the suction areas of the plurality of suction holes arranged in the circumferential direction of the suction roll to improve the suction effect, 3. The microporous film manufacturing device according to claim 1, wherein the lateral grooves are formed so that both ends in the width direction are larger than the film contact area on the surface of the suction roll.

[0020] According to a preferred embodiment of the present invention, the suction roll has suction holes, horizontal grooves, and vertical grooves that exceed the width of the film, thereby stabilizing the suction force across the film product portion and the edge portions at both ends, and suppressing the propagation of the tension difference between the product portion and the edge portions at the cutting section, thereby avoiding film tearing and improving manufacturing efficiency.

[0021] The longitudinal grooves and the lateral grooves are each formed at multiple locations, 7. The microporous film manufacturing device according to claim 1, wherein the longitudinal grooves and the transverse grooves have a width of 1 mm or less.

[0022] According to a preferred embodiment of the present invention, by making the width of the grooves in the width direction and circumferential direction of the suction roll 1 mm or less, the suction force is stabilized across the film product portion and the edge portions at both ends, and the propagation of the tension difference between the product portion and the edge portions at the cutting section is suppressed, thereby avoiding film tearing and improving manufacturing efficiency.

[0023] The lateral grooves are formed at multiple locations, 8. The microporous film manufacturing apparatus according to claim 7, wherein the transverse grooves are arranged at equal intervals in the circumferential direction of the suction roll, and the intervals are 20 mm or more.

[0024] According to a preferred embodiment of the present invention, the transverse grooves in the width direction of the suction roll are arranged at intervals of 20 mm or more around the circumference of the roll, thereby stabilizing the suction force across the film product portion and the edge portions at both ends, and suppressing the propagation of the tension difference between the product portion and the edge portions at the cutting section, thereby avoiding film tearing and improving manufacturing efficiency.

[0025] The longitudinal grooves are formed at multiple locations, The microporous film manufacturing apparatus according to claim 1, claim 2, claim 6, claim 7 or claim 8, wherein the longitudinal grooves are arranged at equal intervals in the width direction of the suction roll, and the intervals are 2 mm or less.

[0026] According to a preferred embodiment of the present invention, the longitudinal grooves in the circumferential direction of the suction roll are arranged at intervals of 2 mm or less in the roll width direction, thereby stabilizing the suction force across the film product portion and the edge portions at both ends, and suppressing the propagation of the tension difference between the product portion and the edge portions at the cutting section, thereby avoiding film tearing and improving manufacturing efficiency.

[0027] A method for producing a microporous film from a long microporous film substrate, comprising: a cutting step of cutting a product portion and both edge portions from the microporous film substrate using a cutting device; a conveying step of conveying the product portion and the edge portion simultaneously; a conveying step of conveying the product and the edge portion separately after the conveying step, A method for producing a microporous film, characterized in that the transport of the product portion and the edge portion is a transport process using at least one drive roll and at least one suction roll from the upstream side.

[0028] According to the microporous film manufacturing method of the present invention, after the edge portions are cut, the product portion and the edge portions are simultaneously conveyed through a drive roll and a suction roll in this order, which prevents the drive roll from transmitting the tension difference between the product portion and the edge portions at the cutting section, thereby preventing film tearing and improving manufacturing efficiency.In addition, because the tension can be appropriately adjusted at the suction roll, the occurrence of wrinkles on the suction roll can be prevented, improving manufacturing efficiency.

[0029] The method for producing a microporous film according to claim 3, characterized in that the absolute value ΔT of the difference between the tension T1 per unit width when transporting the product portion and the tension T2 per unit width when transporting the edge portion is 15 N / m or less.

[0030] According to a preferred embodiment of the present invention, when the absolute value ΔT of the difference between the tension T1 per unit width for conveying the product portion and the tension T2 per unit width for conveying the edge portion is 15 N / m or less, the propagation of the tension difference can be suppressed, thereby avoiding film tearing and improving manufacturing efficiency.

[0031] 5. The method for producing a microporous film according to claim 3, wherein the microporous film has a Gurley air resistance of 10 to 1000 seconds / 100 ml, a porosity of 25% or more, and an average pore size of the micropores of 15 to 200 nm.

[0032] According to a preferred embodiment of the present invention, there is provided a method for producing a microporous film, wherein the microporous film has a Gurley air resistance of 10 to 1000 seconds / 100 ml, a porosity of 25% or more, and an average pore size of the micropores of 15 to 200 nm. [Effects of the Invention]

[0033] According to the present invention, as will be described below, it is possible to obtain an apparatus and method for producing a microporous film that can prevent wrinkling and tearing and can produce a microporous film with high productivity. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic side view of one embodiment of the present invention; [Figure 2] 1 is a schematic vertical cross-sectional side view showing a suction roll according to an embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view showing a suction roll according to one embodiment of the present invention. [Figure 4] FIG. 10 is a schematic side view showing the configuration of a comparative example of a manufacturing device, in which the product portion and the edge portion are transported separately via free rolls and suction rolls after cutting. [Figure 5] This is a schematic side view showing the configuration of a comparative example manufacturing device, a conventional technology in which after cutting, the product portion and the edge portion are transported separately via two drive rolls arranged in an S-shape (S-wrap mechanism). [Figure 6] FIG. 1 is a schematic front view showing a suction roll according to an embodiment of the present invention. [Figure 7] 1 is a schematic longitudinal / lateral cross-sectional view showing a groove shape of a suction roll according to one embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0036] (Explanation of the long length) In the present invention, the term "long" refers to a length that is at least about five times the width of the film. Preferably, the length is 10 times or more. It refers to a material that is long enough to be rolled up and stored or transported.

[0037] In the present invention, the traveling direction or conveying direction refers to the direction in which the microporous film is conveyed toward the product portion winding roll, and the width direction refers to the direction perpendicular to the traveling direction. The product portion winding roll is defined as the most downstream, and the process before that is defined as the upstream.

[0038] FIG. 1 is a schematic side view of a cutting device, conveying device, conveying and winding device for a product portion, and conveying and recovering device for a selvage portion, which are essential parts of a microporous film manufacturing apparatus according to an embodiment of the present invention.

[0039] The microporous film F to be transported through the microporous film manufacturing apparatus exemplified here may be formed by any method. A preferred example is obtained by kneading a molten polyolefin resin with a solvent in an extruder, then discharging the resulting gel sheet from a die onto a cooling drum, optionally undergoing a stretching and orientation process, and then washing and drying to remove the solvent. Alternatively, a polyolefin resin kneaded with a crystal nucleating agent may be discharged from a die onto a cooling drum, and micropores may be formed by controlling the crystal structure without using a solvent. Alternatively, micropores may be formed by combining a heat-resistant polymer, such as polyamide or polyimide, with a solvent having a different compatibility, and then extruding or coating the resulting film. Furthermore, a heat-resistant coating may be applied to one or both sides of the microporous film F made from the polyolefin resin, as appropriate, as long as the air permeability of the micropores is maintained. Alternatively, the film may be formed as an accumulation of synthetic fibers, such as paper or nonwoven fabric.

[0040] The microporous film F thus obtained is preferably stretched uniaxially or biaxially as appropriate to control the pore structure and achieve strength.

[0041] The volatile components remaining in the microporous film after the solvent has been washed and dried are removed from the dried film after the diluent has been removed. Various methods can be used to remove the washing solvent, such as heat drying or air drying. The washing solvent conditions for removing the volatile components can be the same as those described in WO2008 / 016174.

[0042] The stretching of the dried membrane (called second stretching or dry stretching; stretching is performed after at least the membrane-forming solvent has been removed) is preferably performed in the width direction. Such stretching causes orientation of the polymer in the membrane. The length in the width direction before the second stretching is called the initial dry width, and the length in the longitudinal direction (MD) is called the initial dry length. An apparatus for the tenter stretching method (second stretching apparatus 60) is described in WO2008 / 016174, and a method similar to this can be used.

[0043] In the second stretching, a stretching ratio of 1.1 to 2.5 in terms of initial dry width ratio is preferable because it improves the uniformity of film quality. In particular, the thickness unevenness in the width direction is uniform, which can suppress wrinkles during the conveying process and film breakage during the cutting process 10, and further improves the product yield in the width direction in the product section.

[0044] In the second stretching, the dried film is subjected to a temperature below Tm, for example, in the range of Tm to the crystal dispersion temperature (Tcd) -30°C. The film is exposed to a temperature in the range of 70°C to 145°C. 120°C to 142°C is preferred, and 125°C to 140°C is more preferred. Note that Tcd and Tm here are values ​​for the polyethylene with the lowest melting point among the polyethylenes used in the extrudate, which are mixed in an amount of 5 parts by weight or more. The crystal dispersion temperature is measured as the temperature for dynamic viscoelasticity measurement characteristics described in ASTM D4065.

[0045] In the second stretching, the stretching speed of the dried film is preferably 3% / sec or more, more preferably 5% / sec or more, and more preferably in the range of 5 to 25% / sec. The upper limit is preferably 50% / sec to prevent breakage.

[0046] The cutting step 10 is a step performed downstream of the drive roll 11, and is a step of cutting the microporous film F that has passed through the drive roll 11 in the direction along the conveyance direction of the film F. In this case, for example, the width of the microporous film F is set to 2000 mm, and the cutting step 10 is performed on both sides of the microporous film F in the width direction to trim (cut off) portions with unstable shape near both edge portions (portions approximately 150 mm from the outermost ends of the microporous film in the width direction).

[0047] The cutting device 20 in the cutting step 10 is disposed between the conveying rolls 11 and 12, as shown in FIG. 1. This cutting device 20 cuts both widthwise edge portions of the microporous film F, which have large variations in thickness and physical properties (mainly Gurley air resistance, porosity, and average pore size). Any method may be used for this cutting device 20. However, to efficiently cut microporous films F with a high pore opening rate and low toughness, a shear cut method is preferred, in which the film is introduced between upper and lower blades and sheared like scissors. Other methods that can be used include score cutting, in which a blade is pressed against a hard metal or ceramic roller to cut the film, and razor blades, which cut the film in the air or on a groove in a roller. Although the cut surface is slightly raised, the film can also be cut by irradiating it with high-energy particles or radiation, such as a laser.

[0048] After being cut by the cutting device 20, the product portion F1 and both edge portions F2 are simultaneously transported via at least one drive roll 12 and at least one suction roll 42 in this order, and then separated. The drive roll 12 transports the microporous film F in a predetermined traveling direction. The drive roll 12 is driven to rotate by a drive source such as a motor (not shown) via a drive transmission means such as a belt or chain. The tension of the microporous film F may be applied by motor torque (not shown). In particular, when transporting a film that is easily torn and has pores that are easily crushed, such as a microporous film, a dancer roller may be used, which can apply tension by pressing pressure and control the tension even at a low tension. In this case, it is preferable to control the speed and rotation speed of the motor.

[0049] The suction roll 42 is disposed downstream of the cutting process 10, and the product portion (microporous film) F1 and edge portions F2 cut and separated in the cutting process 10 are guided in this order to the drive roll 12 and the suction roll 42, as shown in Fig. 1. As shown in Figs. 2 and 3, the suction roll 42 is provided with a substantially cylindrical rotating roll 42 having a large number of suction holes 43 penetrating from the inside to the outside, and a suction duct 44 disposed inside the rotating roll 42.

[0050] The outer diameter of the suction roll 42 can be, for example, about 300 mm. The angle β, which defines the angle range for the suction roll 42 to adsorb the product portion F1 and the edge portion F2, is preferably 45° or greater, more preferably 90° or greater, to enhance the adsorption of the microporous film F, which must be transported at low tension, to the suction roll 42. The angle β is also called the wrap angle or embrace angle, and is the central angle of a sector formed by the center of the roll and the arc on the roll connecting the point where the film begins to contact the roll and the tent where the film separates from the roll, when viewed as a circle from the roll axial direction.

[0051] The suction duct 44 is connected to a suction device (vacuum device) (not shown) that generates negative pressure, and sucks the product portion F1 and the edge portion F2 through the suction holes 43 of the rotating roll 42. The product portion F1 and the edge portion F2 are sucked by the suction roll 42 within the range of the wrap angle β and are transported.

[0052] The surface of the suction roll 42 has horizontal grooves 46 that are continuous in the roll width direction in order to keep the suction force of the continuous suction holes 43 constant over an area that exceeds the film being transported. Furthermore, with only the lateral grooves 46, the suction force is constant in the grooved portions in the roll width direction, but is not constant in the roll circumferential portions where there are no lateral grooves. Therefore, by providing the longitudinal grooves 48 that are continuous in the roll circumferential direction, the suction force can be kept uniform not only in the roll width direction but also in the roll circumferential direction, stabilizing the suction force across the film product portion and the edge portions at both ends, and suppressing the propagation of the tension difference between the product portion and the edge portions at the cut portion, thereby preventing film tearing and improving production efficiency. The continuous suction holes 43, horizontal grooves 46, and vertical grooves 48 are provided over an area exceeding the film being transported in order to maintain uniform suction force on the product portion F1 and the independent edge portions F2 at both ends.

[0053] The suction force in the roll width direction can be kept constant by setting the width of the transverse grooves 46 and the longitudinal grooves 48 to 1 mm or less. The groove width here refers to the distance from the end 46b or 48b of the groove that is in contact with the film to the end 46c or 48c of the next groove that is in contact with the film, as shown in Figure 7.

[0054] The lateral grooves 46 are arranged at equal intervals around the roll circumference, with the lateral groove interval 47 being preferably 20 mm or more, and more preferably 30 mm or more. The lateral groove interval 47 makes it possible to maintain a constant suction force. The groove interval here refers to the distance from the end 47a of one groove that is in contact with the film to the end 47c of the next groove that is in contact with the film, as shown in Figure 7.

[0055] The longitudinal grooves 48 are arranged at equal intervals in the roll width direction, and the longitudinal groove interval is preferably 2 mm or less. The suction force can be further maintained constant by providing the longitudinal groove interval 49. The groove interval here refers to the distance from the end 49a of one groove that is in contact with the film to the end 49c of the next groove that is in contact with the film, as shown in Figure 7.

[0056] The product portion F1, which is sucked and transported by the suction roll 42, reaches the transport roll 13. The edge portions F2, which are sucked and transported by the suction roll 42, reach the transport roll 15.

[0057] The conveying rolls 13 and 15 are disposed downstream of the suction roll 42 and may be drive rolls or free rolls. The conveying roll 13 conveys (guides) the product portion F1 to the product portion winding roll 50, and the conveying roll 15 conveys (guides) the selvage portion F2 to the selvage portion recovery device. The product portion winding roll 50 winds up the product portion F1 with a predetermined tension, and the selvage portion recovery device conveys and recovers the selvage portion F2 with a predetermined tension. The selvage portion recovery device may be a recovery method in which the selvage portion F2 is wound up by a winding roll. The tension of the selvage portion F2 may be controlled by a selvage portion winding roll, or by a method in which tension is controlled by a nip roll or a drive roll. Furthermore, experiments by the present inventors have revealed that in the cutting process 20, it is preferable that the absolute value ΔT (=|T1-T2|) of the difference between the product part tension T1 conveying the product part F1 and the ear part tension T2 conveying the ear part F2 be 15 N / m or less.

[0058] Although the above description only covers one edge F2 of the two edge portions of the microporous film F, the other edge portion is also provided with the same devices as the cutting step 10, conveying roll 15, and edge recovery device. In addition, at least one driving roll is provided as a conveying roll in the conveying path between the cutting device 20 and the suction roll 42.

[0059] The product section F1 take-up roll 50 is supported by a take-up shaft or chuck and rotates around its own central axis driven by a drive source such as a motor (not shown). After passing through the near roller 14, the microporous film F is wound up as the take-up roll 50 at a predetermined tension. To ensure wrinkle-free winding while aligning the end faces of the take-up roll 50, it is essential to apply a predetermined tension. In this case, the tension of the product section F1 can be controlled by controlling the torque of a drive source such as a motor (not shown). Alternatively, the speed of the drive source (not shown) can be controlled, and tension can be applied by applying pressure to the film, such as a dancer roller or air floater, as part of the upstream conveying process. Because the microporous film F is relatively fragile and its pores are easily crushed, the tension value is preferably set lower than that of typical non-porous films, preferably between 1 N / m and 50 N / m. A tension below 1 N / m can cause the film to sag. Furthermore, friction in the drive unit can significantly impair mechanical tension control. Furthermore, if the stress exceeds 50 N / m, the above-mentioned tearing and collapse of holes are likely to occur.

[0060] The tension is preferably set lower than that of general resin films, from the viewpoint of easily avoiding film tearing or hole collapse due to loosening in the transport rolls or loss of tension control, and is more effective, for example, in the range of 1 N / m to 30 N / m.

[0061] More preferably, the tension value is set in the range of 5 N / m to 25 N / m, which makes it easier to prevent tearing and loosening while controlling the tension of the machine with appropriate precision.

[0062] Therefore, in the cutting process 10 of the present invention, by configuring the cutting device 20, drive roll 12, and suction roll 42 in this order from upstream, the problems of tearing due to the propagation of the absolute value ΔT of the tension difference between the product section F1 and the edge section F2 to the cutting device 20 and tearing due to wrinkles in the suction roll 42 can be solved.

[0063] Microporous films are required to have the ability to allow gases or liquids to permeate through the micropores depending on the application. In particular, for the separators for lithium-ion secondary batteries described above, the electrolyte permeability is generally measured indirectly based on the air permeability.

[0064] Here, air permeability can be represented by Gurley air resistance (seconds / 100 ml) based on JISP8117 (2001). Gurley air resistance is the time it takes for 100 ml of air to pass through a microporous film when pressed at a constant pressure; the higher the air permeability, the smaller the Gurley air resistance value.

[0065] The Gurley air resistance measured by the above-described measurement method is preferably in the range of 10 to 1000 seconds / 100 ml, thereby enabling the film to exhibit electrolyte permeability useful as a separator for batteries and capacitors. A Gurley air resistance of 10 seconds / 100 ml or higher maintains adequate insulation, reducing the risk of short-circuiting when used as a separator. Furthermore, the strength is ensured, making it easier to prevent film tearing during transport when combined with the cutting device of the present invention. On the other hand, a Gurley air resistance of 1000 seconds / 100 ml or lower ensures permeability, preventing the film from impeding the necessary gas and liquid permeability. In particular, when used as a separator for a lithium ion secondary battery, electrolyte permeability is maintained, allowing the battery to be charged and discharged quickly. By employing the above-described cutting device 10 as a method for producing such a microporous film, wrinkles and tears can be avoided even in a microporous film that has high functionality and is effective as a separator for a battery, etc.

[0066] There are several possible methods for measuring the porosity of a microporous film, but in the measurement method of the present invention, a predetermined amount of the film is sampled, and the volume Va of the resin portion is calculated from its weight and the density of the resin constituting the film, and the volume Vb is calculated from the measured film thickness, width, and length, and is then calculated using Equation 1. The thickness of the film can be determined continuously, preferably on a conveying roller, using a light-emitting / receiving or reflective laser sensor. Other methods that can be used include using a radiation or infrared sensor, or sampling a wound film and measuring it with a dial gauge under a low load.

number

[0067] The porosity of the microporous film of the present invention measured using the above-mentioned measuring device and conditions is 25% or more. When the film is used as a battery separator, a certain degree of electrolyte permeability is ensured, enabling rapid charging and discharging of the battery. On the other hand, a porosity of 50% or less can prevent the risk of short circuiting when used as a separator, and can also help to some extent to prevent the film from tearing during transport.

[0068] In the present invention, the "average pore size of the micropores" may be measured by any method, but can be measured using the following measuring device under the following conditions. Measuring instrument: Automatic pore size distribution measuring instrument manufactured by POROUS MATERIALS, Inc. "PERM-POROMETER" Test liquid: 3M "Fluorinert" FC-40 Test temperature: 25℃ Test gas: air Analysis software: Capwin Measurement conditions: Capillary Flow Porometry - Automatic measurement using the default conditions of Wet up, Dry down Conversion formula: d=Cγ / P×10^3 d: pore diameter (nm), C: constant, γ: surface tension of Fluorinert (16 mN / m), P: pressure (Pa)

[0069] The average pore size of the microporous film of the present invention measured using the above-mentioned measuring device and conditions is 15 to 200 nm. When the average pore size is 15 nm or more, when the film is used as a battery separator, electrolyte permeability is ensured to a certain extent, enabling rapid charging and discharging of the battery. On the other hand, when the film is used as a separator, the risk of short circuiting can be prevented and tearing of the film during transport can be more easily avoided to some extent.

[0070] The thickness of the microporous film can be measured continuously on a transport roll, preferably using a light-emitting / receiving or reflective laser sensor. Other methods that can be used include using a radiation or infrared sensor, or sampling a wound film and measuring it with a dial gauge under a low load.

[0071] The thickness of the microporous film of the present invention measured using the above-mentioned measuring device and conditions is 1 μm or more and 50 μm or less. When the thickness is 50 μm or less, which is suitable for a separator of a secondary battery or capacitor, tearing is likely to occur due to stress concentration caused by the propagation of tension differences, particularly at wrinkles and cut sections, and therefore cutting step 10 of the present invention can be suitably applied.

[0072] As a result, the production line is less likely to be stopped due to film breakage, and the production efficiency of the microporous film can be improved. [Example]

[0073] The results of producing a microporous film for a secondary battery separator using the above-described microporous film production method will be described. [Example 1]

[0074] A polymer blended with polyethylene and liquid paraffin as a plasticizer was extruded through a die to form a sheet. The sheet was then simultaneously biaxially stretched 5x5 times, and the plasticizer was washed away in a washing process. The sheet was then stretched 1.5 times in the width direction in a second stretching process to obtain a microporous film F. The resulting film was then cut in a cutting process 10 including a conveying roll as shown in Figure 1 to produce a product part F1 winding roll 50. The microporous film had a Gurley air resistance of 100 seconds / 100 ml, a porosity of 50%, an average pore size of 100 nm, and a thickness of 20 μm. The thickness was measured using a light-emitting / receiving laser sensor, and the porosity was calculated based on the measured thickness using Equation 1.

[0075] As shown in Figure 1, after the second stretching process, the film was cut with a shear cutter at positions 150 mm from each end to separate it into a product portion and an edge portion. The product portion and edge portion were then transported, in order, by one drive roll and one single suction roll, respectively, after which only the product portion F1 was wound up, and only the edge portions were transported and collected. At this time, the absolute value of the difference between the transport tension T1 of the product portion and the transport tension T2 of the edge portions, ΔT = |T1 - T2|, was 10 N / m.

[0076] The conditions for producing the microporous film were a conveying speed of 10 m / min, a conveying tension of 25 N / m, a product width of 2000 mm, and the film roll was taken out by an automatic rewinder every 1000 m of winding length.

[0077] The above combination conditions are summarized in Table 1. The suction roll used here has suction holes, horizontal grooves, and vertical grooves.

[0078] [Example 2] In Example 1, film F was cut with a shear cutter at positions 150 mm from each end, and then the product portion and both edge portions were transported between two drive rolls and one single suction roll, and then only the product portion F1 was taken up, and only the edge portions were transported and collected. At this time, the absolute value of the difference between the transport tension T1 of the product portion and the transport tension T2 of the edge portions, ΔT = |T1 - T2|, was 10 N / m.

[0079] [Example 3] In contrast to Example 1, the product part F1 was wound up so that the absolute value ΔT = |T1 - T2| of the difference between the conveying tension T1 of the product part and the conveying tension T2 of the selvage part was 15 N / m to produce a microporous film.

[0080] [Example 4] In Example 1, product part F1 was wound up to have a Gurley air resistance of 50 seconds / 100 ml, a porosity of 70%, and an average pore size of 150 nm, to produce a microporous film.

[0081] [Example 5] In Example 1, product part F1 was wound up to have a Gurley air resistance of 500 seconds / 100 ml, a porosity of 25%, and an average pore size of 15 nm, to produce a microporous film.

[0082] [Comparative Example 1] Film F, the same as in Examples 1, 2, and 3, had a Gurley air resistance of 100 seconds / 100 ml, a porosity of 50%, and an average pore size of 100 nm. Film F was cut with a shear cutter at positions 150 mm from both ends of film F, and the product portion and both edge portions were transported in this order by one drive roll and one single suction roll. Then, only product portion F1 was wound up, and only the edge portions were transported and collected. At this time, product portion F1 was wound up so that the absolute value ΔT = |T1 - T2| of the difference between the transport tension T1 of the product portion and the transport tension T2 of the edge portions was 20 N / m, thereby producing a microporous film.

[0083] Comparative Example 2 Film F, which had the same Gurley air resistance as in Examples 1, 2, and 3 as in Examples 1, 2, and 3, and a Gurley air resistance of 100 seconds / 100 ml, a porosity of 50%, and an average pore size of 100 nm, was cut with a shear cutter at positions 150 mm from both ends of film F, and the product portion and both edge portions were each transported by a single suction roll, after which only product portion F1 was wound up, and only both edge portions were transported and collected. At this time, product portion F1 was wound up so that the absolute value ΔT = |T1 - T2| of the difference between the transport tension T1 of the product portion and the transport tension T2 of the edge portions was 5 N / m, thereby producing a microporous film.

[0084] Comparative Example 3 Film F, the same as in Examples 1, 2, and 3, had a Gurley air resistance of 100 seconds / 100 ml, a porosity of 50%, and an average pore size of 100 nm. Film F was cut with a shear cutter at positions 150 mm from both ends of film F, and the product portion and both edge portions were transported in this order onto one free roll and one single suction roll. Then, only product portion F1 was wound up, and only the edge portions were transported and collected. At this time, product portion F1 was wound up so that the absolute value ΔT = |T1 - T2| of the difference between the transport tension T1 of the product portion and the transport tension T2 of the edge portions was 5 N / m, thereby producing a microporous film.

[0085] Comparative Example 4 Film F, which was the same as in Examples 1, 2, and 3 and had a Gurley air resistance of 100 seconds / 100 ml, a porosity of 50%, and an average pore size of 100 nm, was cut using a shear cutter at positions 150 mm from both ends of film F.The product portion and both edge portions were then transported using two drive rolls arranged in an S-shape, and product portion F1 was wound up so that the absolute value ΔT = |T1-T2| of the difference between the transport tension T1 of the product portion and the transport tension T2 of the edge portions was 10 N / m, thereby producing a microporous film.

[0086] Here, the method for judging "wrinkles" was as follows: if wrinkles that occurred in the conveying section reached the suction roll 42 and caused tearing, they were judged as "X"; if wrinkles were observed in the conveying section but not on the suction roll 42, they were judged as "△"; and if they were not, they were judged as "○".

[0087] Regarding the method for judging "breakage," if a break occurred during transportation within a roll length of 1,000 m, it was judged as "X," if a break occurred even once during transportation within a roll length of 90,000 m, it was judged as "△," and otherwise it was judged as "○."

[0088] Table 3 shows the results of verification using the suction rolls listed in Table 2.

[0089] As shown in Table 3, in Examples 6 and 7, by setting the groove width and spacing to a preferred value, the suction force is stabilized and the propagation of the tension difference between the product part and the edge part at the cut section is suppressed, thereby preventing film tearing and improving manufacturing efficiency.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3] [Industrial Applicability]

[0093] The manufacturing apparatus and manufacturing method of the present invention are not limited to polyolefin battery separator films, but are also suitable for manufacturing processes for coating separators, nonwoven battery separators, capacitor films, MLCC release films, polyolefin microporous films used for high-precision filtration, etc.

Claims

1. A microporous film manufacturing apparatus for cutting an elongated microporous film substrate along a traveling direction of the microporous film substrate into edge portions at both ends and a microporous film that is a product portion in the center, to obtain the product portions from the microporous film substrate, comprising: a cutting device that cuts the edge portion and the product portion of the microporous film substrate; at least one substrate conveying roll and at least one suction roll for simultaneously conveying the cut product portion and the edge portion; a product portion conveying roll that conveys the cut product portion separately from the edge portion; and an edge transport roll that transports the edge portion after cutting separately from the product portion, the substrate transport roll is a drive roll, The microporous film manufacturing apparatus, wherein the cutting device, the substrate conveying roll, the suction roll, and the product section conveying roll are arranged in this order from the most upstream side to the downstream side in the conveying direction of the microporous film substrate.

2. The microporous film manufacturing apparatus according to claim 1, further comprising a stretching device that includes grippers that grip both widthwise ends of the long microporous film substrate upstream of the cutting device in the conveying direction of the microporous film substrate and that stretches the microporous film with the grippers.

3. The suction roll has suction holes formed at a number of locations on the surface of the suction roll in the longitudinal direction and the circumferential direction, the suction holes being connected to a negative pressure source; transverse grooves formed on the surface of the suction roll to connect the suction areas of the suction holes arranged along the length of the suction roll to improve the suction effect; and longitudinal grooves formed on the surface of the suction roll to connect the suction areas of the plurality of suction holes arranged in the circumferential direction of the suction roll to improve the suction effect, The microporous film manufacturing apparatus according to claim 1 or 2, wherein the lateral grooves are formed so that both ends in the width direction are larger than the film contact area on the surface of the suction roll.

4. The longitudinal grooves and the lateral grooves are each formed at multiple locations, The microporous film manufacturing apparatus according to claim 3, wherein the longitudinal grooves and the transverse grooves have a width of 1 mm or less.

5. The lateral grooves are formed at multiple locations, The microporous film manufacturing apparatus according to claim 4, wherein the transverse grooves are arranged at equal intervals in the circumferential direction of the suction roll, and the intervals are 20 mm or more.

6. The longitudinal grooves are formed at multiple locations, The microporous film manufacturing apparatus according to claim 3 or 4, wherein the longitudinal grooves are arranged at equal intervals in the width direction of the suction roll, and the intervals are 2 mm or less.

7. A method for producing a microporous film product from a long microporous film substrate, comprising: a cutting step of cutting a product portion and both edge portions from the microporous film substrate; a conveying step of conveying the product portion and the edge portion simultaneously, A method for producing a microporous film, characterized in that the transport of the product portion and the edge portion is a transport process using at least one drive roll and at least one suction roll from the upstream side to the downstream side in the transport direction of the microporous film substrate.

8. The method for producing a microporous film according to claim 7, characterized in that the absolute value ΔT of the difference between the tension T1 per unit width when the product portion is transported separately from the selvage portion and the tension T2 per unit width when the selvage portion is transported separately from the product portion is 15 N / m or less.

9. The method for producing a microporous film according to claim 7 or claim 8, wherein the microporous film has a Gurley air resistance of 10 to 1000 seconds / 100 ml, a porosity of 25% or more, and an average pore size of the micropores of 15 to 200 nm.

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