JP2016042446A - Polyolefin microporous film wound body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elongated polyolefin microporous film wound body by which the winding can be performed smoothly by preventing a winder from being suddenly stopped in a battery assembly process, and which is suitable for transportation to a high-temperature region.SOLUTION: A polyolefin microporous film wound body comprises: a polyolefin microporous film; and a terminal end detection tape attached to the polyolefin microporous film near an end of the film on the side where the film winding is started. The wound body has a winding length of 1500 m or larger. The terminal end detection tape includes: an adhesive layer made of an adhesive; and a base material. The adhesive layer is 5-30 μm in thickness on one entire surface of the base material, which is provided within a range of 10-40% to 100% of the total thickness of the terminal end detection tape.SELECTED DRAWING: Figure 2

Description

The present invention relates to a polyolefin microporous membrane roll.

  It is known that a lithium ion secondary battery uses a wound electrode body in which a positive electrode and a negative electrode are overlapped via a separator and wound in a spiral shape. In the process of manufacturing the wound electrode body, there is a winding process in which the separator is fed from the state of the wound body and supplied, overlapped between the positive electrode and the negative electrode, and wound by the winding device.

  In the winding process, the winding device suddenly stops when the member reaches the end, and it is necessary to prevent the impact on the device caused by this. For that purpose, it is preferable that the stop position is detected before the end of the member is reached, and the winding device stops gently. In addition, once the winding device stops before it is finished as a wound electrode body, the wound electrode body wound halfway cannot be used for a battery, and the stop position is strictly controlled from the viewpoint of productivity. It is required to do. Therefore, in order to control the stop position, for example, marking that indicates that the end is near the end of the winding body of the separator is performed, and a display tape is one of the specific methods of marking. Attaching is done. The detection method of the display tape is generally detected by light reflectance and transmittance.

  Battery separators, especially lithium ion battery separators, are interposed between the positive electrode and negative electrode to ensure electrical insulation between the electrodes, excellent ion permeability, and pore closure when temperature rises inside the battery Thus, a polyolefin microporous membrane having a so-called shutdown function that interrupts the flow of current is suitably used.

  In Patent Document 1, as a means for detecting the stop position of the separator and automatically stopping the winding device, a display tape is attached to the separator at a position 2 to 4 m from the winding core, and the display tape is detected. A method of stopping the winding device before reaching the end of the separator is described. And in the polyolefin wound body which stuck the display tape comprised from the adhesive layer which consists of an adhesive agent, and a substrate, the protrusion of the adhesive agent from the display tape which arises by contraction of the polyolefin microporous film is made into the edge part of the substrate concerned It is disclosed that by not providing an adhesive layer, adhesion between the polyolefin microporous film (lower layer) to which the display tape is attached and the polyolefin microporous film (upper layer) wound thereon is prevented.

JP 2009-295500 A

  In the manufacturing process of the wound body electrode, it is preferable to reduce the number of times each member is changed in order to improve the working efficiency, and it is required to make the winding length of the polyolefin microporous membrane wound body longer. However, when the winding length is increased, the winding thickness of the wound body increases, so that the pressure applied to the detection tape rises and the adhesive easily protrudes from the detection tape. And the lower polyolefin microporous membrane adhere to each other, whereby the polyolefin microporous membrane wound body in which the upper and lower polyolefin microporous membranes adhere may cause the winding device to stop suddenly.

  In recent years, production bases for lithium-ion secondary batteries have tended to expand southward in southern China and Southeast Asia. Considering that the temperature during transportation rises due to supply to areas with high temperatures, and that it may be stored in a container yard for several days, it is assumed that the temperature in metal shipping containers will be 60 ° C or higher. Is done. When exposed to high temperatures for a long time, the polyolefin microporous membrane tends to shrink, and as a result, the pressure of the wound body rises (winding up due to shrinkage) and the fluidity increases from the detection tape affixed to the wound body It becomes easy for the adhesive to stick out.

  An object of the present invention is to provide an elongated polyolefin microporous membrane wound body suitable for transportation to a high temperature area, which can smoothly wind by preventing a sudden stop of the winding device in the battery assembly process. And

In order to solve the above problems, the wound body of the present invention has the following configuration.
1. A wound body made of a polyolefin microporous film, wherein the polyolefin microporous film is affixed with a detection tape, has a winding length of 1500 m or more, and the detection tape comprises a base material and an adhesive layer made of an adhesive. The pressure-sensitive adhesive layer has a thickness of 5 to 30 μm on one whole surface of the base material, and is provided in a range of 10 to 40% with the total thickness of the detection tape being 100%. Porous membrane wound body.
2. 2. The polyolefin microporous membrane roll according to 1 above, wherein the pressure-sensitive adhesive has an adhesive strength of 1.1 N / 10 mm or less.
3. The polyolefin microporous film roll according to 1 or 2, wherein the substrate of the detection tape is polypropylene.

  ADVANTAGE OF THE INVENTION According to this invention, the winding body of the elongate polyolefin microporous film suitable for the transportation to a high temperature area can be provided.

Fig.1 (a) is a perspective view which shows one Embodiment of the polyolefin microporous film winding body which concerns on embodiment of this invention. FIG. 1B is an enlarged schematic side sectional view of a polyolefin microporous membrane roll. It is a schematic side surface enlarged view which shows one Embodiment in the polyolefin microporous film winding body of the tape for a detection which concerns on embodiment of this invention. It is a schematic side surface enlarged view which shows one Embodiment of the tape for a detection which concerns on embodiment of invention.

A wound body according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing an embodiment of a polyolefin microporous membrane roll according to an embodiment of the present invention. FIG. 1A schematically shows a state in which a winding start end portion 2 (hereinafter also referred to as an end) of the polyolefin microporous membrane 1 is fixed to a winding core 3 with a double-sided tape 4 and a detection tape 5 is attached. . FIG. 1 (b) schematically shows a state (polyolefin microporous film wound body 8) in which the polyolefin microporous film 1 of FIG. As shown in FIG. 1 (a) and FIG. 1 (b), the polyolefin microporous membrane 1 constituting the polyolefin microporous membrane wound body 8 has a detection tape 5 on a part of the polyolefin microporous membrane in the length direction. Affixed. The detection tape 5 includes a base material 6 and an adhesive layer 7 made of an adhesive provided on one whole surface of the base material.

  At the time of manufacturing the lithium ion battery, the polyolefin microporous membrane roll 8 is drawn out from the feed-out end 9 and taken up by the winding device together with the positive electrode and the negative electrode. At that time, the detection tape 5 attached to the polyolefin microporous membrane 1 is detected by the detector, so that the stop position can be notified and the sudden stop of the winding device can be prevented. The detection tape 5 for detecting the end can be informed of the end of the polyolefin microporous membrane by being attached at a position 2 to 4 m from the winding start end 2 of the polyolefin microporous membrane. The detection tape 5 informs the stop position, and the stop position is not limited to the end. Moreover, the detection tape 5 should just be affixed so that it can detect with a detector, and is affixed on any one surface or both surfaces of the surface of a polyolefin microporous film.

  Fig.2 (a) shows the schematic side surface enlarged view of the state of the tape for a detection in the winding body which consists of a polyolefin microporous film of this invention. The detection tape 5 is affixed to the surface opposite to the core side of the polyolefin microporous membrane 10 (lower layer), and the wound polyolefin microporous membrane 11 (upper layer) is positioned on the detection tape 5. A polyolefin microporous membrane 10 (lower layer), a detection tape 5 attached to the polyolefin microporous membrane 10 (lower layer), and a polyolefin microporous membrane 11 (upper layer) wound on the detection tape 5 are formed. A small space 12 exists. FIG. 2B is a schematic enlarged side view of the state of the detection tape in the wound body made of the polyolefin microporous film under a high temperature condition. Although the adhesive having increased fluidity protrudes from the detection tape due to an increase in the high temperature and the winding pressure, the presence of the space 12 allows the polyolefin microporous film 10 (lower layer) and the polyolefin microporous film 11 (upper layer) to adhere to each other. It is hard to do.

  Hereinafter, embodiments of the present invention will be further described. In addition, these description and Examples illustrate this invention, and do not restrict | limit the scope of the present invention.

1. Detection Tape The detection tape used in the present invention includes a base material and an adhesive layer made of an adhesive provided on one entire surface of the base material.

  The total thickness of the detection tape is preferably as thin as possible, and is preferably 100 μm at the maximum, more preferably 60 μm or less, and even more preferably 35 μm or less. By making the total thickness within the above preferred range, in particular, it prevents the polyolefin microporous film (upper layer) wound on the detection tape from being marked with a step due to pressure, and suppresses damage to the polyolefin microporous film. be able to.

  The length in the width direction of the detection tape is not particularly limited as long as it is a length detected by a detector, but is preferably 10 mm or more, and more preferably 20 mm or more. The upper limit is preferably 100 mm, more preferably 50 mm, and even more preferably 30 mm or less in order to prevent wrinkles from occurring when the tape is applied.

  The thickness of the pressure-sensitive adhesive layer is preferably 5 to 30 μm, more preferably 5 to 20 μm, and still more preferably 5 to 15 μm. By adjusting the thickness of the pressure-sensitive adhesive layer to the above preferred range, the pressure-sensitive adhesive can be prevented from protruding or the amount of protrusion can be minimized. Moreover, it can prevent that a tape peels with the force at the time of cutting a polyolefin microporous film (it is called a slit).

  The thickness of the adhesive layer is preferably 10 to 40%, more preferably 10 to 30%, still more preferably 10 to 20%, with the total thickness (total thickness) of the detection tape being 100%. By setting the thickness of the adhesive layer within the above preferred range, the polyolefin microporous membrane (lower layer) to which the detection tape is attached, the polyolefin microporous membrane (upper layer) positioned on the detection tape, and the detection tape are provided. Even if the pressure-sensitive adhesive protrudes into the space to be formed (the space 12 in FIG. 2A), it becomes difficult for the pressure-sensitive adhesive to contact both the upper layer and the lower layer, and adhesion between the upper layer and the lower layer can be prevented.

  Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, and silicon-based pressure-sensitive adhesives. In particular, an acrylic pressure-sensitive adhesive having low fluidity is preferable.

  The adhesive strength of the adhesive is preferably 1.1 N / 10 mm or less, more preferably 0.6 N / 10 mm or less, and still more preferably 0.1 N / 10 mm or less. By setting the adhesive strength of the pressure-sensitive adhesive within the above preferred range, even when the pressure-sensitive adhesive protrudes, the adhesive strength is such that the adhesion between the polyolefin microporous membrane (lower layer) and the polyolefin microporous membrane (upper layer) can be removed by the winding device. Thus, the sudden stop of the winding device can be prevented.

  Examples of the material of the base material include resins such as polyolefin, polyester, polyimide, and vinyl chloride. In particular, when polypropylene, which is a polyolefin, is used, curling of the detection tape can be suppressed even when placed under high temperature storage conditions. When stored at a high temperature, the polypropylene substrate and the polyethylene microporous membrane have substantially the same linear expansion coefficient (thermal expansion coefficient), and similarly shrink and hardly curl. If the detection tape is curled, there is a risk of misalignment during conveyance, or erroneous detection of a sensor that detects the detection tape may be caused.

2. Polyolefin microporous membrane As the polyolefin microporous membrane in the present invention, a polyolefin microporous membrane used as a battery separator can be used. Although not particularly limited, a polyolefin microporous membrane (lower layer) and a polyolefin microporous membrane (upper layer) ) Is preferably 0.5% or more, and more preferably 1% or more. The heat resistance of the polyolefin porous membrane can be determined from the average value of the rate of change relative to the initial dimension of MD when stored in an oven at 105 ° C. for 8 hours.

  Examples of the polyolefin component forming the polyolefin microporous film include crystalline homopolymers, copolymers and blends thereof obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and the like. Etc. Of these, polypropylene, polyethylene, and compositions thereof are preferred.

As an example of the method for producing the polyolefin microporous membrane, a method for producing a microporous membrane from the polyolefin composition will be described.
By supplying and kneading a liquid low-volatile solvent (a good solvent for the polyolefin composition) in the molten state in the middle of the extruder containing the polyolefin composition in the molten state, a high concentration of the polyolefin composition having a uniform concentration is obtained. Prepare a concentrated solution. Next, a heated solution of this polyolefin composition is extruded from a die and molded. In the case of a sheet die, the die gap is usually 0.1 to 5.0 mm, the extrusion temperature is 140 to 250 ° C., and the extrusion speed is Usually, molding is performed at 1 m to 10 m / min.

  Thus, the sheet | seat of the polyolefin composition solution extruded from the die | dye is cooled, and a gel-like sheet | seat is obtained. Cooling is performed to at least the gelation temperature or lower. As a cooling method, a method of directly contacting cold air, cooling water, or another cooling medium, a method of contacting a roll cooled by a refrigerant, or the like can be used.

  This gel-like sheet is heated and stretched at least in a uniaxial direction by a usual tenter method, roll method, rolling method, or a combination of these methods. Among these, biaxial stretching is preferable, and any of longitudinal and transverse simultaneous stretching or sequential stretching may be used.

  The stretching temperature ranges from the melting point of the polyolefin composition to about 10 ° C. or less, preferably from the crystal dispersion temperature to less than the melting point, and in the case of the polyethylene composition, it is 90 to 140 ° C. Although a draw ratio changes with thickness of a gel-like sheet | seat, it is at least 2 times or more in a uniaxial direction, 10 times or more by a surface magnification, Preferably it is 15 to 400 times.

  The obtained stretched film is washed with a volatile solvent, and the remaining low-volatile solvent is removed. Cleaning solvents include hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as ethane trifluoride, and ethers such as diethyl ether and dioxane. Use volatile. These volatile solvents are appropriately selected according to the low-volatile solvent used for dissolving the polyolefin composition, and used alone or in combination. The cleaning method can be performed by a method of immersing and extracting in a volatile solvent, a method of showering a volatile solvent, or a method using a combination thereof.

  The above washing is performed until the residual low-volatile solvent in the stretched film is less than 1% by weight. Thereafter, the cleaning solvent is dried. The cleaning solvent can be dried by heat drying, air drying, or the like. The microporous membrane obtained by drying is preferably heat-set within the temperature range of the crystal dispersion temperature to the melting point.

3. Preparation of wound body of polyolefin microporous film Polyolefin microporous film formed by a manufacturing apparatus is wound on a winding core as a raw material. Usually, since the raw film of the polyolefin microporous film formed has a width of several hundred mm to several m, it is cut (slit) in order to meet the customer's required width.

  For the cutting, an ordinary slitting machine is used, the raw material of the polyolefin microporous film attached to the slitting machine is fed out, and the polyolefin microporous film cut to the customer's required width is wound on a winding core to obtain a wound body. For example, the winding start end of the polyolefin microporous membrane is fixed to the winding core using a double-sided tape, and winding is started. In the vicinity of the winding start end (fixed position), specifically, 2 to 4 m from the winding start end. At the position of the customer, the end of the polyolefin microporous membrane wound body is affixed with a detector to detect the end of the tape, the slit is started, the winding length required by the customer is wound on the core, and the polyolefin A microporous membrane roll can be produced. Since the detection tape only needs to be able to detect that the stop position is close, it may be affixed to the same length as the width of the polyolefin microporous membrane of the wound body, or shorter than the width of the polyolefin microporous membrane. It may be affixed.

  As the winding length of the polyolefin microporous membrane is longer, the number of customer changes is reduced. Therefore, in the polyolefin microporous membrane roll of the present invention, the length of the polyolefin microporous membrane is preferably 1500 m or more, more preferably 2000 m. As mentioned above, More preferably, it is 3000 m or more.

  The larger outer diameter of the core is preferably 88.5 mm or more, more preferably 150 mm or more, and further preferably 200 mm or more. The number of turns of the polyolefin microporous film wound around the core is preferably 8000, more preferably 7000, and even more preferably 5000.

The total thickness of the detection tape, the thickness of the adhesive layer, and the adhesive strength of the adhesive were measured by the following methods.
1. Total thickness of detection tape A 10 cm × 2.5 cm detection tape was affixed to a polypropylene sheet whose thickness was measured in advance, and the total thickness of the polypropylene sheet and the detection tape was measured at 9 points using a film thickness meter. The value obtained by subtracting the thickness of the polypropylene sheet from the total thickness of the polypropylene sheet and the detection tape is taken as the measurement value of the total thickness of the detection tape, and 5 points are obtained by removing 2 points from the maximum value and 2 points from the minimum value. An average value was calculated from the measured values to obtain the total thickness of the detection tape.

2. Adhesive Layer Thickness The adhesive of the detection tape was removed with toluene using a solvent, and the thickness of the substrate film was measured at 9 points. The average value was calculated from the measured values of 5 points excluding 2 points from the maximum value and 2 points from the minimum value, and the value obtained by subtracting the thickness of the base material from the total thickness of the detection tape was used as the thickness of the adhesive layer. .

3. The adhesive strength of the adhesive was measured according to JIS-Z0237.

The presence or absence of adhesion and the curl height were evaluated by the following methods.
4). Presence / absence of adhesion The presence / absence of adhesion between the polyolefin microporous film (lower layer) and the polyolefin microporous film (upper layer) due to protrusion of the pressure-sensitive adhesive of the detection tape at a high temperature in the polyolefin microporous film roll was evaluated. Three rolls of polyolefin microporous membrane wound body after slitting are stored in an oven at 70 ° C. for 24 hours, taken out, and the polyolefin microporous membrane wound body cooled to room temperature is drawn out with a tension of 5.0 g / 100 mm, and the tape for detection If the upper layer and the lower layer film adhere with the sticking adhesive and the feeding stops, it will be rejected (x (with adhesion)), otherwise it will pass (○ (without adhesion)). did.

5. Curled height After the slit product is stored in an oven at 70 ° C. for 24 hours, it is cooled to room temperature, cut from the surface of the product to the nearest point of the detection tape, and then the adhesion is evaluated and taken out. As shown in FIG. 3, as for the curled state of the slit cross section of 2.5 mm or more, 2.5 mm or more as a raised height per tape width of 25 mm is rejected (X), and less than 2.5 mm is passed (OK) and observed. The results are shown in Table 1.

Example 1
Using an ABS core with an outer diameter of 88.5 mm, apply a 7 μm polyolefin microporous membrane (heat shrinkage 3%) to a slitting machine, attach the microporous membrane after slitting to the core with double-sided tape, and start winding The end detection tape was affixed at a position 2 m from the part, and the slit microporous film was wound up 2000 m to produce a product reel. The used end detection tape uses a polypropylene film with a thickness of 40 μm for the base material, and an adhesive with an adhesive strength of 0.55 N / 10 mm is applied to the adhesive with a thickness of 16 μm. A 29% adhesive tape was used.

Example 2
The used end detection tape uses a polypropylene film with a thickness of 25 μm as the base material, and an adhesive with an adhesive strength of 1.06 N / 10 mm is applied to the adhesive with a thickness of 7 μm. The state of the end detection tape was observed in the same manner as in Example 1 except that a 22% adhesive tape was used.

Example 3
The used end detection tape uses a polypropylene film with a thickness of 40 μm for the base material, and an adhesive with an adhesive strength of 0.50 N / 10 mm is applied to the adhesive with a thickness of 18 μm. The state of the end detection tape was observed in the same manner as in Example 1 except that an adhesive tape having a layer ratio of 31% was used.

Example 4
The used end detection tape uses a polypropylene film with a thickness of 38 μm for the base material, and an acrylic adhesive with an adhesive strength of 0.03 N / 10 mm is applied to the adhesive with a thickness of 5 μm. The state of the end detection tape was observed in the same manner as in Example 1 except that a 12% adhesive tape was used.

Comparative Example 1
The used tape for end detection uses a polypropylene film with a thickness of 30 μm for the base material, and an acrylic adhesive with an adhesive strength of 3.48 N / 10 mm is applied to the adhesive with a thickness of 25 μm. The state of the end detection tape was observed in the same manner as in Example 1 except that 45% adhesive tape was used.

Comparative Example 2
The used end detection tape uses a polypropylene film with a thickness of 40 μm for the base material, and an adhesive with an adhesive strength of 2.32 N / 10 mm is applied to the adhesive with a thickness of 18 μm. The state of the end detection tape was observed in the same manner as in Example 1 except that an adhesive tape having a layer ratio of 31% was used.

Comparative Example 3
The used end detection tape is a 25 μm thick polyester film as the base material, and the adhesive is coated with an acrylic adhesive with an adhesive strength of 1.20 N / 10 mm at a thickness of 25 μm. The state of the end detection tape was observed in the same manner as in Example 1 except that a 50% adhesive tape was used.

1: Polyolefin microporous membrane 2: Winding end (end)
3: winding core 4: double-sided tape 5: end detection tape 6: base material of end detection tape 7: adhesive layer of end detection tape 8: polyolefin microporous film roll 9: feeding end 10: polyolefin fine Porous membrane (lower layer)
11: Polyolefin microporous membrane (upper layer)
12: Space formed between end detection tape, polyolefin microporous membrane (lower layer) and polyolefin microporous membrane (upper layer)

Claims (3)

A wound body comprising a polyolefin microporous film, wherein the polyolefin microporous film has a detection tape affixed thereto, and has a winding length of 1500 m or more, and the detection tape comprises an adhesive layer made of an adhesive and a substrate The polyolefin is provided with a thickness of 5 to 30 μm on one whole surface of the base material and a thickness of 10 to 40% with the total thickness of the detection tape as 100%. A microporous membrane wound body. The polyolefin microporous membrane roll according to claim 1, wherein the pressure-sensitive adhesive has an adhesive strength of 1.1 N / 10 mm or less. The said porous film winding body of Claim 1 or Claim 2 whose base material of the said tape for a detection is a polypropylene.

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