JP2014118552A - Method of manufacturing propylene-based resin micropore film, and winding device of propylene-based resin micropore film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a propylene-based resin micropore film having an even thickness and even gas permeability which is suitable for a separator of a lithium ion battery requiring a high output.SOLUTION: A propylene-based resin film extruded from an extruder is winded in a roll-form around a diameter-expandable/contractible winding core while the diameter of the winding core is contracted. When heating the rolled propylene-based resin film to cure in a heating device, the winding core is energized in a diameter-expanding direction with spring power so as to absorb the elongation of the propylene-based resin film due to heating by expanding the diameter of the winding core, and when cooling, the shrinkage of the propylene-based resin film is absorbed by contracting in diameter, so that wrinkles caused by sagging from the winding core when stretching are not generated on the rolled propylene-based resin film.

Description

  The present invention relates to a method for producing a propylene-based resin microporous film suitably used for a separator of a lithium ion battery, and a winding device for a propylene-based resin film used in a curing step in this production method.

  As a separator for a lithium ion battery, a microporous film of an olefin resin mainly composed of polyethylene is widely used. This is because when a lithium ion battery abnormally generates heat due to a short circuit or the like, the polyethylene constituting the microporous film melts in a temperature range of about 130 ° C., and the microporous structure is blocked (shutdown), so that lithium ions This is because abnormal heat generation of the battery can be stopped to ensure safety.

  As a method for producing such a propylene-based resin microporous film, conventionally, as described in, for example, Patent Document 1 and Patent Document 2, a propylene-based resin film extruded from a T-die attached to an extruder The propylene-based resin constituting the propylene-based resin film is crystallized by cooling to produce a lamella, and this propylene-based resin film is subsequently wound around a cylindrical core made of paper tube in a roll shape. After a curing process for growing lamellae by performing heat treatment in a heating apparatus such as a heating furnace or a hot stove, it is cooled to room temperature and then stretched while unwinding the propylene-based resin film to remove the non-lamellar. There is a known method for obtaining a propylene-based resin microporous film in which cracks are generated in a crystal part and an infinite number of microporous parts are formed. To have.

JP 7-216118 A Japanese Patent Laid-Open No. 10-100344

  In the manufacturing method of the propylene-based resin microporous film, when the roll-wrapped propylene-based resin film wound around the cylindrical core is subjected to heat treatment in the heating device during the curing process performed subsequent to the extrusion process. Because the linear expansion coefficient due to heating of the propylene-based resin film is larger than that of the core, the roll diameter of the roll-propylene-based resin film is larger than the diameter of the core, and the roll-wrapped propylene-based resin film is caused by its own weight. The lower peripheral part hangs down from the lower outer peripheral surface of the winding core, and a slight gap is generated between the lower peripheral outer peripheral surface of the winding core and the lower peripheral inner peripheral surface of the roll-propylene-based resin film. become.

  When the propylene-based resin film is cooled after curing in this state, the propylene-based resin film contracts, the roll diameter of the roll-wrapped propylene-based resin film is reduced, and the lower end portion of the roll-wrapped propylene-based resin film hanging from the core is Due to the contraction, it is deformed into a buckling shape and a recumbent is generated. This recumbent appears every turn when the roll-wrapped propylene-based resin film is unwound from the core during the stretching process, and when the recumbent is stretched, the formation of micropores is insufficient compared to the normal part. Thus, when a microporous film is formed in a non-uniformly formed propylene-based resin microporous film, and this propylene-based resin microporous film is used in a lithium ion battery separator, a portion having a high lithium ion permeability and a portion having a low lithium ion permeability are obtained. As a result, dendrites are generated in a highly permeable region, and a short circuit is likely to occur, which causes problems in the life and long-term safety of the separator.

  Also, in the above curing process, if the roll-wrapped propylene resin film is heat-treated in the heating device, the temperature and the amount of hot air are likely to be uneven in the heating device. When curing without rotating in the direction, the entire circumference cannot be cured at a uniform temperature, making it difficult to uniformly grow the lamella produced on the propylene-based resin film during the extrusion process. As a result, the thickness, air permeability, and heat shrinkage rate of the resulting propylene-based resin microporous film are non-uniform, making it difficult to employ a separator for a lithium ion battery that requires high output.

  The present invention has been made in view of such problems, and the object thereof is a propylene-based resin having a uniform thickness and air permeability that can be suitably used as a separator for a lithium ion battery requiring high output. It is in providing the manufacturing method of a microporous film, and the apparatus for implementing this method.

  In order to achieve the above object, the method for producing a propylene-based resin microporous film of the present invention, as described in claim 1, supplies propylene-based resin to an extruder, melts and kneads it, Extruding a propylene-based resin film from the attached T-die, cooling the propylene-based resin film, a curing step of winding the extruded propylene-based resin film around a core and performing a heat treatment in a heating device, and curing After the process, the propylene resin film is unwound from the core and uniaxially stretched to form an infinite number of micropores in the propylene resin film, and an annealing process to anneal the stretched propylene resin film In the sequential production method of propylene-based resin microporous film, the curing process is applied to a core that can be expanded and contracted in diameter. Wrap the len-based resin film in a roll shape, put this roll-wrapped propylene-based resin film in a heating device, and urge the core in the diameter-expanding direction to absorb the elongation of the propylene-based resin film due to heating It is characterized by comprising.

  Further, the invention according to claim 2 is characterized in that the curing is performed while rotating the roll-wrapped propylene-based resin film wound around the winding core at a constant peripheral speed in the curing step.

  The invention according to claim 3 is a winding device for a propylene-based resin film for carrying out a curing step in the method for producing a propylene-based resin microporous film, and is a rectangular curve curved in an arc shape in the width direction. A core formed in a cylindrical shape that can be expanded and contracted in the radial direction by combining a plurality of plate pieces, a rotating shaft disposed at the center of the core, and the diameter of the core is increased with a constant pressure. A biasing mechanism that biases in the direction, and a stopper member that holds the core in a reduced diameter state against the biasing force of the biasing mechanism when winding the propylene-based resin film, and releases the holding after winding It is characterized by comprising.

  In the winding device configured as described above, the invention according to claim 4 is a spring receiver in which the urging mechanism for urging the winding core in the diameter-enlarging direction is fixed to the center portion of the rotating shaft, and the spring receiver. Left and right sliders arranged in the center on the rotation shaft so as to be slidable in the length direction of the rotation shaft, and left and right compression springs interposed between opposing surfaces of the spring receiver and the left and right sliders; The inner ends of the sliders are pivotally attached to the outer peripheral surfaces of the left and right sliders, and the outer ends are pivotally attached to the inner peripheral surfaces of the curved plate pieces forming the winding core. And a plurality of inclined pivot arms that reduce the diameter of the core when moving toward each other and increase the diameter of the core when moved away from each other. Slidably fit on the rotating shaft and press the outer end surfaces of the left and right sliders. Characterized in that it is constituted by a short cylindrical body of.

  On the other hand, in the invention according to claim 5, the urging mechanism for urging the core in the diameter increasing direction is provided at several places on the rotating shaft facing the inner surface of each curved plate piece forming the core. From cylinders standing and fixing radially toward each core, and piston bodies pressed by springs press-fitted into these cylinders and pressing the tip surfaces thereof to the inner surfaces of the curved plate pieces Further, the stopper member is constituted by an end lid that is movably disposed on the rotation shaft and detachably engages with both end openings of the winding core.

  The invention according to claim 6 relates to still another structure of the urging mechanism and the stopper member, wherein the urging mechanism is arranged so as to be opposed to the inner surface of each curved plate piece forming the winding core. The spring support members attached at several locations and the outer peripheral surfaces of these spring support members and the inner peripheral surfaces of the curved plate pieces forming the core are connected to constantly bias the core in the direction of diameter reduction. The outer peripheral surface of the tension spring that is slidable on the rotary shaft is engaged with the tapered surface formed on the inner peripheral surface of the open end of the core in a wedge shape, and approaches each other. And a pair of left and right wedge members that expand the diameter against the tensile force of the tension spring when moved in the direction, and the left and right wedge members are slidably fitted to the rotating shaft. These short cylinders are pressed against the outer end surface of these, and the pressing force is adjusted for these short cylinders. Characterized in that it is pressed by the possible compression spring.

  According to the method for producing a propylene-based resin microporous film according to claim 1, when the propylene-based resin crystallizes by an extrusion process and a lamella is grown by a curing process, The propylene-based resin film that has undergone the extrusion process is wound into a roll shape on a core that can be expanded and contracted in diameter, and this roll-wrapped propylene-based resin film is placed in a heating device to urge the core in the diameter-expanding direction. Since the expansion of the propylene-based resin film due to heating is absorbed by the diameter of the core, the roll-wrapped propylene-based resin film does not hang down from the core and maintains the state of being wound around the outer surface of the core without any gaps. The propylene-based resin film can be cured while the crystallization portion (lamellar) and non-crystallized in the extrusion direction of the propylene-based resin film. A lamellar structure in which crystal parts are alternately and evenly arranged can be formed, and by uniaxially stretching this propylene-based resin film in the stretching process, a large number of micropores penetrate the film front and back surfaces uniformly. Propylene-based resin microporous film having excellent air permeability and low air-permeability variation can be obtained, and this propylene-based resin microporous film is used as a separator for a lithium ion battery. As a result, it is possible to stably produce a lithium ion battery with uniform power generation performance, and to provide a lithium ion battery that can stably exhibit high power generation performance even in high output applications.

  Furthermore, according to the method for producing a propylene-based resin microporous film of the present invention, as described in claim 2, in the curing step, the roll-wrapped propylene-based resin film wound around the core is fixed to a certain circumference. Curing is carried out while rotating at a speed, so even if temperature unevenness or hot air flow unevenness occurs inside the heating device, the roll-wrapped propylene-based resin film should be kept at a uniform temperature from the surface to the inside. It is possible to cure the rolled propylene-based resin film at a uniform temperature, and to uniformly grow the lamellae in the propylene-based resin film. The thickness, air permeability, and heat shrinkage rate are uniform. A certain propylene-based resin microporous film can be produced.

  According to the invention which concerns on Claim 3, as a winding apparatus of the propylene-type resin film for implementing the curing process in the manufacturing method of the said propylene-type resin microporous film, the rectangular-shaped curve curved in the arc shape in the width direction A core formed in a cylindrical shape that can be expanded and contracted in the radial direction by combining a plurality of plate pieces, a rotating shaft disposed at the center of the core, and the diameter of the core is increased with a constant pressure. A biasing mechanism that biases in the direction, and a stopper member that holds the core in a reduced diameter state against the biasing force of the biasing mechanism when winding the propylene-based resin film, and releases the holding after winding Therefore, when winding the propylene-based resin film extruded from the extruder, the propylene-based resin film is smoothly wound around the core while keeping the core diameter reduced by the stopper member. At the time of the curing process, by releasing the holding by the stopper member, the winding core is urged in the diameter increasing direction by the urging mechanism to automatically absorb the elongation of the propylene-based resin film due to heating. It can be cured with a propylene resin film wound around the outer peripheral surface of the core without a gap, and crystallized parts and non-crystalline parts are alternately and evenly arranged in the extrusion direction of the propylene resin film. A propylene-based resin microporous film having an arrayed lamellar structure can be obtained.

  According to the invention of claim 4 in the core device configured as described above, a spring receiver in which the urging mechanism for urging the core in the diameter increasing direction is fixed to the central portion of the rotating shaft, and the spring Left and right sliders arranged slidably in the length direction of the rotary shaft on the rotary shaft with the receiver in the center, and left and right compression springs interposed between the spring receiver and the left and right sliders facing each other When the inner ends of the sliders are pivotally attached to the outer peripheral surfaces of the left and right sliders, and the outer ends are pivotally attached to the inner peripheral surfaces of the curved plate pieces forming the winding core, a plurality of inclined rotations are possible. Further, the stopper member is configured by a short cylindrical body that presses and receives the outer end surfaces of the left and right sliders by sliding and fixing the stopper member to the rotation shaft. Press the member against the left and right sliders to bring these left and right sliders closer to each other By moving in the direction, the right and left compression springs are compressed, and the tilting rotary rod is rotated in the slanting direction, so that the diameter of the winding core can be easily and reliably reduced and the reduced diameter is maintained. The propylene-based resin film can be wound, and if the left and right stopper members are retracted after being wound, the winding core is repressed in the direction in which the tilting rotary rod is raised by the restoring force of the compression spring. Can be energized in the diameter-expanding direction, and a heat treatment or the like can be performed while maintaining the propylene-based resin film wound in a roll shape in a tension state.

  According to the invention which concerns on Claim 5, the said urging | biasing mechanism is stood and fixed to several places of the rotating shaft facing the inner surface of each curved plate piece which forms the winding core radially toward each winding core. And a piston body that is pressed by a spring press-fitted into these cylinders and presses the front end surface thereof against the inner surface of each curved plate piece. Since it is configured by an end lid that is movably disposed on the core and detachably engages with both ends of the core, when the propylene-based resin film is wound around the core, the end lid This stopper member can be smoothly wound while holding the core in a reduced diameter state. After winding, the stopper member is unlocked from both ends of the core by releasing the stopper member. Forms the winding core by restoring force The core is urged in diameter direction, can be subjected to a heat treatment or the like with tension holds the propylene resin film wound into a roll oppressed each curved plate pieces are.

  According to the invention which concerns on Claim 6, the said urging | biasing mechanism is attached to several places of a rotating shaft facing the inner surface of each curved plate piece which forms the winding core, These spring support A tension spring that connects the outer peripheral surface of the member and the inner peripheral surface of each curved plate piece forming the core, and constantly urges the core in the direction of diameter reduction, and is slidable on the rotating shaft When the outer peripheral surface is wedge-engaged with the tapered surface formed on the inner peripheral surface of the open end of the core and moved in a direction approaching each other, the core is pulled by the tensile force of the tension spring. And a pair of left and right wedge members that are expanded in diameter against each other, and further comprising a short cylindrical body in which a stopper member is slidably fitted to the rotating shaft and pressed against the outer end surfaces of the left and right wedge members. Since these end cylinders are pressed by a compression spring whose pressing force can be adjusted, The winding diameter of the core can be easily adjusted to a desired diameter by moving the left and right wedge members in the direction of approaching and separating from each other on the rotating shaft, and therefore the core is held in a reduced diameter state. However, the propylene-based resin film can be wound around the winding core, and after being wound, the pressing force of the short cylindrical body that presses the outer end surfaces of the left and right wedge members through the compression spring is pulled as described above. By making it larger than the tensile force of the spring, the core can be urged in the diameter-expanding direction, and heat treatment or the like can be performed while keeping the propylene-based resin film wound in a roll shape in a tensioned state.

The partial exploded perspective view of the film winding apparatus used at the time of curing. The simplified longitudinal front view of the state which reduced the diameter of the core. The simplified longitudinal side view. The simplified longitudinal front view of the state which expanded the core diameter. The simplified longitudinal side view. The partially exploded perspective view which shows another form of a film winding apparatus. The simplified longitudinal front view of the state which reduced the diameter of the core. The simplified longitudinal side view. The simplified longitudinal front view of a state in which the diameter of the winding core is expanded. The simplified longitudinal side view. The partially exploded perspective view which shows another form of a film winding apparatus. The simplified longitudinal front view of the state which reduced the diameter of the core. The simplified longitudinal side view. The simplified longitudinal front view of a state in which the diameter of the winding core is expanded. The simplified longitudinal side view.

  Next, an embodiment of the method for producing a propylene-based resin microporous film of the present invention will be described in the order of steps of an extrusion process, a curing process, a stretching process, and an annealing process. In addition, as a propylene-type resin which comprises a propylene-type resin microporous film, a propylene homopolymer, the copolymer of a propylene and another olefin, etc. are mentioned, for example. Propylene-type resin may be used independently, or 2 or more types may be used together. The copolymer of propylene and other olefins may be either a block copolymer or a random or polymer.

(Extrusion process)
After the propylene-based resin is supplied to the extruder and melt-kneaded, an extrusion process is performed to obtain a propylene-based resin film by extrusion from a T die attached to the tip of the extruder.

  When the temperature of the propylene-based resin when melt-kneading the propylene-based resin with an extruder is low, the resulting propylene-based resin film (film F wound in a roll on a winding device in FIGS. 2 to 5) If the thickness of the propylene-based resin film is not uniform, or the surface smoothness of the propylene-based resin film is lowered and high, the orientation of the propylene-based resin may be lowered, and the propylene-based resin may not produce lamellae. Preferably, the temperature is 20 ° C. higher than the melting point and 100 ° C. higher than the melting point of the propylene resin, preferably 25 ° C. higher than the melting point of the propylene resin and 80 ° C. higher than the melting point of the propylene resin. It is more preferable that the temperature is lower than the temperature.

  Furthermore, if the draw ratio when extruding the propylene resin into a film from an extruder is small, the tension applied to the propylene resin is reduced, resulting in insufficient molecular orientation of the propylene resin, and the propylene resin causes lamellae. There is a possibility that it may not be generated sufficiently. In addition, when the draw ratio when extruding a propylene-based resin into a film from an extruder is large, the molecular orientation of the propylene-based resin becomes high, but the film-forming stability of the propylene-based resin film is lowered and obtained. There is a possibility that the thickness accuracy and width accuracy of the propylene-based resin film may be lowered. Therefore, the draw ratio when the propylene-based resin is extruded from the extruder into a film is preferably 50 to 300, more preferably 65 to 250, and particularly preferably 70 to 250. The draw ratio means a value obtained by dividing the clearance of the lip of the T die by the thickness of the propylene-based resin film extruded from the T die.

  In addition, if the film forming speed of the propylene resin film is low, the tension applied to the propylene resin is lowered, the molecular orientation of the propylene resin is insufficient, and the propylene resin may not generate lamellae sufficiently. If it is large, the molecular orientation of the propylene-based resin is high, but the film-forming stability of the propylene-based resin film is lowered, and the thickness accuracy and width accuracy of the resulting propylene-based resin film are lowered. / Min is preferable, 15 to 250 m / min is more preferable, and 15 to 30 m / min is particularly preferable.

  Then, the propylene resin film constituting the propylene resin film is cooled by cooling the propylene resin film extruded from the T-die until the surface temperature becomes 100 ° C. or lower than the melting point of the propylene resin. Crystallizes to produce lamellae. In the present invention, the propylene-based resin film is cooled by extruding the propylene-based resin film constituting the propylene-based resin film by extruding the melt-kneaded propylene-based resin, and then cooling the propylene-based resin film. It is possible to promote the generation of lamella in the portion where the is oriented.

  The surface temperature of the cooled propylene-based resin film is preferably not more than 100 ° C. lower than the melting point of the propylene-based resin, more preferably 140 to 110 ° C. lower than the melting point of the propylene-based resin, and more than the melting point of the propylene-based resin. Also, a temperature lower by 135 to 120 ° C. is particularly preferable. When the surface temperature of the cooled propylene-based resin film is high, the propylene-based resin constituting the propylene-based resin film cannot be crystallized, and there is a possibility that a lamella is not generated.

(Curing process)
Subsequently, the propylene-type resin film obtained by the extrusion process mentioned above is cured. This curing process for the propylene-based resin film is performed in order to grow the lamella formed in the propylene-based resin film in the extrusion process. Thereby, it is possible to form a laminated lamella structure in which crystallized portions (lamellar) and amorphous portions are alternately arranged in the extrusion direction of the propylene-based resin film. It is possible to generate a crack between lamellas, not within the lamella, and to form a minute through hole (microhole part) starting from this crack.

  In the method of the present invention, the curing of the propylene-based resin film is performed by first winding the propylene-based resin film obtained in the extrusion step into a roll shape to obtain a rolled propylene-based resin film F.

  1 to 5 show an example of a winding device, and a plurality of (six in the drawing) rectangular curved plate pieces 1a, 1a... 1a curved in an arc shape in the width direction are combined. The core 1 is formed in a cylindrical shape that can be expanded and contracted in the radial direction by means of the above, the rotary shaft 2 disposed at the center of the core 1, and the core 1 is urged in the diameter increasing direction with a constant pressure. And a stopper member 4 for holding the core 1 in a reduced diameter state against the urging force of the urging mechanism 3 when winding the propylene-based resin film and releasing the holding after winding. And consists of

  The urging mechanism 3 includes a spring receiver 31 fixed to the central portion of the rotating shaft 2 in the length direction, and is slidably fitted to both side portions of the rotating shaft 2 with the spring receiver 31 in the center. Cylindrical left and right sliders 32, 32, left and right compression springs 33, 33 interposed between the spring receiver 31 and the opposing surfaces of the left and right sliders 32, 32, and the left and right sliders, respectively. The inner end of each of the outer peripheral surfaces of 32 and 32 is pivotally attached to each of the outer peripheral surfaces. The outer end is inclined radially outwardly toward the opening ends on both sides of the core 1 toward the outer end. Rotating arm rods 34, 34,... 34 pivotally attached to the inner surface of the end of each curved plate piece 1a of the winding core 1, and the left and right sliders 32, 32 are directed toward the spring receiver 31. When moving in a direction approaching each other, all the tilting and rotating arms 34 are directed toward the center so that they fold their umbrellas. When the core 1 is reduced in diameter and the left and right sliders 32 and 32 are moved away from each other, all the tilting and rotating arms 34 stand outward to open the umbrella. Thus, the winding core 1 is configured to expand in diameter.

  As shown in FIG. 3, the left and right sliders 32, 32 project from the outer peripheral surface of the rotary shaft 2 on the inner peripheral surface of a groove 2a formed in the longitudinal direction of the rotary shaft 2. The protruding ridge 32a is fitted and slid only in the length direction of the rotating shaft 2, and the rotation of the rotating shaft 2 is caused by the engaging force between the grooves 2a and the protruding portion 32a to move the inclined rotating arm rod 34. It is comprised so that it may transmit to the core 1 via.

  Further, the stopper members 4 and 4 are formed of short cylinders slidably fitted to both end portions of the rotary shaft 2 on the back side of the left and right sliders 32 and 32, and between the inner and outer peripheral surfaces thereof. A screw hole 4a is provided through the screw hole 4a, and a screw 4b is screwed into the screw hole 4a. The screw 4b is screwed and its tip is pressed against the outer peripheral surface of the rotary shaft 2, so that these left and right stoppers The members 4 and 4 are configured to be fixed to the rotary shaft 2.

  In order to wind up the propylene-based resin film obtained in the extrusion process into a roll using the winding device configured as described above, first, the left and right stopper members 4 and 4 are moved to the left and right as shown in FIG. The stopper members 4, 4 are moved toward the fixed spring receiver 31 at the center of the rotating shaft while being pressed against the back surfaces of the sliders 32, 32, respectively. By this movement, the left and right compression springs 33, 33 are compressed, and the rotating arm rod 34 connecting the left and right stopper members 4 and the plurality of curved plate pieces 1a forming the core 1 is bent down. Rotating in the direction, the core 1 is reduced in diameter. After reducing the diameter of the core 1 to a predetermined diameter in this way, the reduced diameter state is maintained by pressing the tip of the screw 4b provided on the stopper member 4 to the outer peripheral surface of the rotating shaft 2.

  The propylene-based resin film extruded from the extruder while rotating the winding core 1 integrally with the rotating shaft 2 by rotating the rotating shaft 2 of the winding device in this state by a rotation driving mechanism (not shown). As shown in FIG. 3, a roll-wrapped propylene-based resin film F is obtained by winding on a core 1, and the roll-wrapped propylene-based resin film F is heated by a heating apparatus (not shown) such as a heating furnace or a hot air furnace. Install inside and cure.

  At this time, if the curing is performed without rotating the roll-wrapped propylene-based resin film F in the heating device, the propylene-based resin film can be cured at a uniform temperature. Therefore, the lamella produced in the propylene-based resin film in the extrusion process cannot be grown uniformly, and the thickness, air permeability, and heat shrinkage force of the resulting propylene-based resin microporous film may be uneven. Therefore, curing is performed while rotating the roll-propylene-based resin film F integrally with the core 1.

  In this way, the propylene-based resin film is cured while rotating the roll-wrapped propylene-based resin film F around the rotation shaft 2 in the circumferential direction integrally with the core 1, thereby causing temperature unevenness and hot air inside the heating device. Even if the air volume unevenness occurs, the roll-wrapped propylene-based resin film F can be brought to a uniform temperature as a whole from the surface to the inside, and the rolled-up propylene-based resin film is cured at a uniform temperature. Thus, the lamellae in the propylene-based resin film can be uniformly grown, and a propylene-based resin microporous film having a uniform thickness, air permeability, and heat shrinkage rate can be manufactured.

  0.05-70 rpm is preferable and, as for the rotation speed of the roll propylene-type resin film F at the time of curing, 0.1-50 rpm is more preferable. If the number of rotations of the roll-wrapped propylene resin film F is too low, the effect obtained by curing while rotating the roll-wrapped propylene-based resin film F may not be sufficient. Further, even if the roll-wrapped propylene-based resin film F is rotated at a rotational speed exceeding 70 rpm, there is a possibility that an effect corresponding to the increase in the rotational speed cannot be obtained.

  The curing temperature of the roll-wrapped propylene-based resin film F is preferably 30 ° C. lower than the melting point of the propylene-based resin and 1 ° C. lower than the melting point of the propylene-based resin, and 25 ° C. lower than the melting point of the propylene-based resin. More preferably, the temperature is lower than the lower temperature and lower than the temperature 5 ° C. lower than the melting point of the propylene resin. When the curing temperature of the roll-wrapped propylene-based resin film F is low, there is a possibility that the lamella cannot be grown sufficiently. Moreover, when the curing temperature of the roll-wrapped propylene-based resin film F is high, the orientation of the propylene-based resin molecules of the propylene-based resin film is relaxed, and the lamella may be broken.

  In addition, the curing temperature of the roll-wrapped propylene-based resin film F is the temperature of the atmosphere in which the roll-wrapped propylene-based resin film F is installed. Therefore, for example, when curing a roll-propylene-based resin film F inside a heating device such as a hot stove, the temperature of the atmosphere in which the roll-propylene-based resin film F is installed inside the heating device is defined as a curing temperature. To do.

  The curing time of the roll-propylene-based resin film F is preferably 1 hour or longer, and more preferably 15 hours or longer. The roll-wrapped propylene-based resin film F is preferably cured for 1 hour or longer so that the temperature of the propylene-based resin film is entirely cured from the surface of the roll-wrapped propylene-based resin film F to the curing temperature described above. And the lamellae of the propylene-based resin film can be grown sufficiently and uniformly. On the other hand, if the curing time is too long, the lamella growth of the propylene resin film corresponding to the increase in the curing time is not expected, and the propylene resin film may be deteriorated by heat. Therefore, the curing time is preferably 35 hours or less, and more preferably 30 hours or less.

  In addition, when the rolled propylene-based resin film F is cured in the heating device, the roll-wrapped propylene-based resin film F expands depending on the curing temperature, and its linear expansion coefficient is larger than that of the paper core 1. When the roll diameter of the propylene-based resin film is larger than the diameter of the core 1, the roll-wrapped propylene-based resin film F hangs down due to its own weight, and when it is cooled after curing, side rolls are generated in the suspending portion and this roll-wrapped propylene-based resin When stretching is performed while the film F is rewound, there is a problem that the air permeability becomes non-uniform. Therefore, the core 1 of the winding device is urged in the diameter-expanding direction and heated during heat curing. And when the expansion is absorbed by expansion, the inner peripheral surface of the roll-wrapped propylene-based resin film F is brought into close contact with the outer peripheral surface of the core 1 without a gap, Even when the roll-wrapped propylene-based resin film F contracts due to cooling after heat curing, the core 1 is reduced in diameter according to the contraction amount, and the roll-propylene-based resin film F is applied to the outer peripheral surface of the core 1. Keep in close contact with no gaps.

  That is, in the winding device in which the roll 1 is wound in the state where the diameter of the core 1 is reduced as described above, the screws 4b of the left and right stopper members 4 and 4 are unscrewed. After releasing the fixing of the stopper members 4 and 4 with respect to the rotating shaft 2, when the left and right stopper members 4 and 4 are retracted and separated from the sliders 32 and 32, the sliders 32 and 32 can freely retract. The restoring force of the left and right compression springs 33 represses all the rotating arm rods 34 through these sliders 32, 32 to urge the winding core 1 in the diameter increasing direction, and expands by heat curing. While expanding the diameter according to the amount of expansion of the roll-wrapped propylene-based resin film F, as shown in FIG. 5, the inner peripheral surface of the roll-wrapped propylene-based resin film F is always kept in close contact with the core 1 without a gap. Can be cured

  Further, when the roll-wrapped propylene-based resin film F contracts by cooling after heat curing, the curved plates 1a forming the core 1 by the contraction pressure cause the rotary arm 34 to bend down and move the sliders 32, 32. Can be moved in the direction approaching each other against the elastic force of the compression springs 33, 33, and the core 1 can be reduced in diameter in accordance with the shrinkage amount of the roll-wrapped propylene-based resin film F. The inner peripheral surface of the resin film F can be kept in close contact with the core 1 without a gap.

  In the curing step, curing is preferably performed while rotating the roll-wrapped propylene-based resin film F in the circumferential direction in a state where the axial center direction is held horizontal. In this way, in the curing process, the roll-propylene-based resin film F is more effective in blocking in the roll-propylene-based resin film F by rotating the propylene-based resin film F with its axial core oriented in the horizontal direction. Can be reduced. The term “horizontal” means substantially horizontal, and includes that the axial direction of the roll-wrapped propylene-based resin film F is within a range of −5 ° to + 5 ° from the horizontal plane.

  In the winding device for winding the propylene-based resin film extruded from the extruder, the mechanism for expanding and contracting the core 1 formed by combining a plurality of curved plate pieces 1a into a cylindrical shape is as described above. An urging mechanism or a stopper member different from the urging mechanism 3 or the stopper member 4 may be employed.

  FIG. 6 to FIG. 10 show an example, and by combining a plurality of rectangular curved plate pieces 1a, 1a... 1a curved in an arc shape in the width direction, a cylindrical shape that can be expanded and contracted in the radial direction is combined. The formed core 1, the rotating shaft 2 disposed at the center of the core 1, an urging mechanism 3A for urging the core 1 in a diameter increasing direction with a constant pressure, and propylene In a winding device comprising a stopper member 4A that holds the core 1 in a reduced diameter state against the urging force of the urging mechanism 3A when winding the resin film, and releases the holding after winding. A plurality of urging mechanisms 3A are erected and fixed radially at several places (three places in the drawing) of the rotating shaft 2 so as to face the curved plate pieces 1a forming the winding core 1. The cylinder 3A-1, the spring 3A-2 press-fitted into the cylinder 3A-1, and the piston pressed by the spring 3A-2 Structure receiver 31 formed by connecting the tip of rod 3A-4 of piston body 3A-3 projecting from cylinder 3A-3 to cylinder 3A-1 to the inner surface of opposing curved plate piece 1a And consists of

  Further, the stopper member 4A has inner peripheral surfaces at both ends of the core 1 having a reduced diameter at the outer peripheral edge of the disc portion 4A-1 whose center portion is slidably fitted to the rotary shaft 2. It consists of an end lid that forms an annular portion 4A-2 that is detachably engaged.

  The winding device configured in this manner compresses a plurality of curved plate pieces 1a with a rotating shaft 2 and a spring 3A-2 in a cylindrical body 3A-1 connecting the curved plate pieces 1a. The core 1 is reduced in diameter by being pushed down toward the rotating shaft 2, and the core 1 is reduced in diameter in this state by fitting the annular portion 4 </ b> A- 2 of the stopper member 4 </ b> A to the outer peripheral surface of the core 1. Keep in state.

  The propylene-based resin film extruded from the extruder while rotating the winding core 1 integrally with the rotating shaft 2 by rotating the rotating shaft 2 of the winding device in this state by a rotation driving mechanism (not shown). 7 and FIG. 8, a roll-wrapped propylene-based resin film F is obtained by winding on a core 1, and this roll-wrapped propylene-based resin film F is heated by a heating apparatus such as a heating furnace or a hot air furnace (FIG. (Not shown) and curing is performed while rotating in the same manner as in the above embodiment.

  Further, at the time of curing, all the cylinders 3A-1 constituting the urging mechanism 3A are removed by removing the stopper members 4A, 4A that are fitted and locked to the openings at both ends of the core 1. The restoring force of the inner spring 3A-2 is applied to all the curved plate pieces 1a constituting the core 1, and the core 1 is urged in the diameter increasing direction. As shown in FIG. 10 by expanding the diameter according to the amount of expansion of the expanded roll-propylene resin film F, the inner circumference surface of the roll-propylene-based resin film F is kept in close contact with the core 1 without any gaps. I do.

  When the roll-wrapped propylene-based resin film F is shrunk by cooling after heat curing, the curved plate piece 1a forming the core 1 is connected between the rotating shaft 2 and these curved plate pieces 1a by the shrinkage pressure. While the spring 3A-2 in the cylindrical body 3A-1 is compressed, the spring 3A-2 is pressed down toward the rotary shaft 2 while the diameter of the core 1 is reduced. It can be kept in close contact with no gap.

  11 to 15 show still another structure of the urging mechanism and the stopper member in the winding device, and rectangular bent plate pieces 1a, 1a, ... 1a curved in an arc shape in the width direction are shown. A winding core 1 formed into a cylindrical shape that can be expanded and contracted in the radial direction by combining a plurality of sheets, a rotating shaft 2 disposed in the center of the winding core 1, and the winding core 1 are expanded with a constant pressure. It comprises a biasing mechanism 3B that biases in the radial direction, and a stopper member 4B that holds the core 1 in a reduced diameter state when winding the propylene-based resin film and releases the holding after winding. In the winding device, the urging mechanism 3B is fixed to several places (two places in the drawing) of the rotary shaft 2, and the outer peripheral surface of these spring support members 3B-1 and the winding Each curved plate piece 1a forming the core 1 is connected to the inner peripheral surface to constantly urge the winding core 1 in the direction of diameter reduction. The tension spring 3B-2 is slidably disposed on both sides of the rotary shaft 2, and the outer peripheral inclined surfaces are fitted into the inner peripheral surfaces of the open ends of the core 1 and rotated in the direction of contacting and separating from each other. A pair of left and right wedge members 3B-3 and 3B-3 formed to expand and contract the core 1 when sliding on the shaft 2 and these wedge members 3B-3 and 3B-3 are directed toward the core 1 side. The compression springs 3B-4 and 3B-4 that are energized by being engaged with the ends of both ends of the rotary shaft 2 so as to be able to advance and retract freely, and the elasticity of these compression springs 3B-4 and 3B-4 is adjusted. It consists of a nut body 3B-5.

  The wedge members 3B-3 and 3B-3 are formed such that the outer peripheral surfaces thereof are inclined surfaces that are inclined in the inner diameter direction from the back surface toward the surfaces facing each other, and the core 1 is formed on the inclined surfaces. A protruding strip 6 is slidably engaged with a tapered groove 5 formed on the inner peripheral surface of each side end portion of each curved plate piece 1a, and the lengthwise direction is provided on the outer peripheral surface of the rotary shaft 2. The protrusion 2 provided on the inner peripheral surface of the central hole of the wedge member 3B-3 fitted to the rotary shaft 2 is engaged with the groove 2a formed in the groove 2a to rotate the rotary shaft 2. Engagement between the grooves 2a and the ridges 7, and provided on the inner peripheral surface of the protrusion 6 and the end of the curved plate piece 1a projecting on the outer peripheral inclined surface of the wedge member 3B-3. It is configured to transmit to the core 1 by engagement with the tapered groove 5.

  The stopper member 4B is formed of a short cylindrical body slidably disposed on the rotary shaft 2 on the back side of the left and right wedge members 3B-3 and 3B-3, and the inner surface of the stopper member 4B is formed on the left and right wedge members 3B. -3 and 3B-3, and the compression springs 3B-4 and 3B-4 are pressed between the opposing surfaces of the stopper members 4B and 4B and the nut bodies 3B-5 and 3B-5. Intervene. In addition, when the stopper members 4B and 4B are retracted and the diameter of the core 1 is reduced to the minimum diameter, a fixing pin 8 is provided on the rotary shaft 2 so that the stopper members 4B and 4B do not retract further. .

  The winding device configured as described above is configured such that when the nut bodies 3B-5 and 3B-5 are screwed back to weaken the elastic force of the compression spring 3B-4, the left and right wedges are pulled by the tensile force of the tension spring 3B-2. The core 1 is reduced in diameter while the members 3B-3 and 3B-3 and the stopper members 4B and 4B are retracted, and the stopper members 4B and 4B reach the fixing pins 8 and 8 to maintain the reduced diameter state.

  The propylene-based resin film extruded from the extruder while rotating the winding core 1 integrally with the rotating shaft 2 by rotating the rotating shaft 2 of the winding device in this state by a rotation driving mechanism (not shown). 12 and 13, a roll-wrapped propylene-based resin film F is obtained by winding it on a core 1, and this roll-wrapped propylene-based resin film F is heated by a heating device such as a heating furnace or a hot air furnace (see FIG. (Not shown) and curing is performed while rotating in the same manner as in the above embodiment.

  Further, during the curing, the nut bodies 3B-5 and 3B-5 are screwed to compress the compression springs 3B-4 and 3B-4, and the elastic members generate wedge members via the stopper members 4B and 4B. 3B-3 and 3B-3 are moved toward each other, and the core 1 is urged in the diameter-expanding direction against the tensile force of the tension spring 3B-2. As shown in FIG. 15, the diameter of the roll-wrapped propylene resin film F is expanded according to the amount of expansion of the expanded roll-propylene-based resin film F. I do.

  When the roll-wrapped propylene-based resin film F contracts by cooling after heat curing, the wedge member 3B-3 and the stopper member 4B are retracted integrally by the contraction pressure, and the roll is wound while the core 1 is reduced in diameter. The inner peripheral surface of the propylene-based resin film F can be kept in close contact with the core 1 without a gap.

(Stretching process)
Subsequently, the extending | stretching process which unwinds the roll wound propylene-type resin film F after a curing process as mentioned above from the core 1, and is uniaxially stretched is performed. This stretching step preferably includes a first stretching step and a second stretching step following the first stretching step. In the first stretching step, the propylene-based resin film is preferably uniaxially stretched only in the extrusion direction.

  In the first stretching step, the lamellae in the propylene-based resin film are hardly melted, and by separating the lamellae by stretching, a fine crack is efficiently generated independently in the non-crystalline part between the lamellae. A large number of micropores are reliably formed starting from this crack.

  In the first stretching step, if the surface temperature of the propylene-based resin film is low, the propylene-based resin film may be broken at the time of stretching, and if it is high, cracks are less likely to occur in the non-crystalline portion between lamellae. -20-100 degreeC is preferable and 0-80 degreeC is more preferable.

  In the first stretching step, when the draw ratio of the propylene-based resin film is small, it is difficult to form micropores in the amorphous portion between the lamellae, and when large, the micropores are uniformly formed in the propylene-based resin microporous film. Since it may not be formed, 1.05 to 2 times is preferable, and 1.1 to 1.8 times is more preferable.

  In addition, in this invention, the draw ratio of a propylene-type resin film means the value which remove | divided the length of the propylene-type resin film after extending | stretching by the length of the propylene-type resin film before extending | stretching.

  If the stretching speed in the first stretching step of the propylene-based resin film is small, it is difficult to form micropores uniformly in the non-crystalline portion between the lamellas. Therefore, 20% / min or more is preferable. Since there exists a possibility that a resin film may fracture | rupture, 20-3000% / min is more preferable, and 20-70% / min is especially preferable. In addition, in this invention, the extending | stretching speed of a propylene-type resin film means the change rate of the dimension in the extending | stretching direction of the propylene-type resin film per unit time.

  The method for stretching the propylene-based resin film in the first stretching step is not particularly limited as long as the propylene-based resin film can be uniaxially stretched. For example, the propylene-based resin film can be stretched at a predetermined temperature using a uniaxial stretching device. Examples thereof include a uniaxial stretching method.

  Next, in the propylene-based resin film after uniaxial stretching in the first stretching step, the surface temperature of the propylene-based resin film is preferably higher than the surface temperature of the propylene-based resin film during uniaxial stretching in the first stretching step. A uniaxial stretching process is performed at a temperature lower than the melting point of the resin by 10 to 100 ° C. (second stretching step). Also in this second stretching step, the propylene-based resin film is preferably uniaxially stretched only in the extrusion direction. Thus, in the first stretching step, the propylene-based resin film is stretched in the same direction as in the first stretching step at a surface temperature higher than the surface temperature of the propylene-based resin film in the first stretching step. Many micropores formed in the propylene-based resin film can be grown.

  In the second stretching step, if the surface temperature of the propylene-based resin film is low, the micropores formed in the propylene-based resin film in the first stretching step are difficult to grow, and the air permeability of the propylene-based resin microporous film is improved. If it is high, the micropores formed in the propylene-based resin film in the first stretching step may be blocked, and instead the air permeability of the propylene-based resin microporous film may be reduced. The temperature is preferably higher than the surface temperature of the propylene-based resin film in the stretching step and 10 to 100 ° C. lower than the melting point of the propylene-based resin, higher than the surface temperature of the propylene-based resin film in the first stretching step and A temperature lower than the melting point by 15 to 80 ° C. is more preferable.

  In the second stretching step, if the stretching ratio of the propylene-based resin film is small, the micropores formed in the propylene-based resin film during the first stretching step are difficult to grow, and the air permeability of the propylene-based resin microporous film is reduced. If it is large, the micropores formed in the propylene-based resin film in the first stretching step may be blocked, and instead the air permeability of the propylene-based resin microporous film may be lowered. 05-3 times are preferable and 1.8-2.5 times are more preferable.

  In the second stretching step, if the stretching speed of the propylene-based resin film is high, micropores may not be uniformly formed in the propylene-based resin film, so 500% / min or less is preferable, and 400% / min or less is preferable. More preferred is 60% / min or less. In the second stretching step, if the stretching speed of the propylene-based resin film is small, it is difficult to form micropores uniformly in the non-crystalline portions between the lamellae, so it is preferable to be 15% / min or more.

  The method for stretching the propylene-based resin film in the second stretching step is not particularly limited as long as the propylene-based resin film can be uniaxially stretched. For example, the propylene-based resin film can be stretched at a predetermined temperature using a uniaxial stretching device. Examples thereof include a uniaxial stretching method.

(Annealing process)
Next, an annealing process is performed in which the propylene-based resin film that has been uniaxially stretched after the curing process is annealed. This annealing step is performed to alleviate the residual strain generated in the propylene-based resin film due to the stretching applied in the above-described stretching step, and to suppress the heat shrinkage caused by heating in the resulting propylene-based resin microporous film. Is called.

  If the surface temperature of the propylene-based resin film in the annealing process is low, the strain remaining in the propylene-based resin film is insufficiently relaxed, and the dimensional stability during heating of the resulting propylene-based resin microporous film is reduced. If it is high, there is a possibility that the micropores formed in the stretching process may be clogged, so that the temperature is higher than the surface temperature of the propylene-based resin film during the second stretching process and the melting point of the propylene-based resin. Is preferably 10 ° C. or lower.

  If the shrinkage rate of the propylene-based resin film in the annealing process is large, the propylene-based resin film may sag and may not be uniformly annealed, or the shape of the micropores may not be maintained, so 30% or less It is preferable to set to. The shrinkage ratio of the propylene-based resin film is obtained by dividing the shrinkage length of the propylene-based resin film in the stretching direction during the annealing step by the length of the propylene-based resin film in the stretching direction after the second stretching step. The value multiplied by.

1 core
1a Curved plate piece 2 Rotating shaft 3 Biasing mechanism 4 Stopper member

Claims (6)

Propylene-based resin is supplied to an extruder, melt-kneaded, the propylene-based resin film is extruded from a T-die attached to the tip of the extruder, and this propylene-based resin film is cooled, and the extruded propylene-based resin film A curing process in which a core is wound and heat-treated in a heating device, and after the curing process, the propylene-based resin film is unwound from the core and uniaxially stretched to form innumerable micropores in the propylene-based resin film In the method for producing a propylene-based resin microporous film in which a stretching process and an annealing process for annealing the stretched propylene-based resin film are sequentially performed, the curing process includes a propylene-based resin film on a core whose diameter can be freely expanded and contracted. Wrap it into a roll, put this roll-wrapped propylene-based resin film in a heating device, and roll it Method for producing a propylene resin microporous film, characterized by being configured to absorb the elongation of the propylene resin film by heating by energizing the diameter direction. The production of a propylene-based resin microporous film according to claim 1, wherein the curing is performed while rotating the roll-wrapped propylene-based resin film wound around the core at a constant peripheral speed during the curing step. Method. A winding core that is formed into a cylindrical shape that can be expanded and contracted in the radial direction by combining a plurality of rectangular curved plate pieces that are curved in an arc shape in the width direction, and a rotating shaft that is disposed at the center of the winding core And an urging mechanism that urges the core in the diameter-expanding direction with a constant pressure, and keeps the core in a reduced diameter state against the urging force of the urging mechanism when winding the propylene-based resin film. And a stopper member that releases the holding after winding, and a propylene-based resin film winding device. The urging mechanism that urges the core in the diameter-expanding direction includes a spring receiver fixed to the central portion of the rotating shaft, and is slidable on the rotating shaft in the length direction of the rotating shaft with the spring receiver as the center. The left and right sliders, the left and right compression springs interposed between the opposing surfaces of the spring receiver and the left and right sliders, and the inner ends of the left and right sliders are pivotally attached to the outer peripheral surfaces. The outer end is pivotally attached to the inner peripheral surface of each curved plate piece forming the core, and when the left and right sliders move in a direction approaching each other on the rotation axis, the diameter of the core is reduced and separated. The stopper member is slidably and fixedly fitted to the rotating shaft so as to expand the diameter of the winding core when moved in the direction. 4. It is comprised by the short cylinder body which presses and receives an outer end surface. Winding device of the propylene-based resin film of the mounting. The urging mechanism for urging the core in the diameter-expanding direction is erected and fixed radially toward each core at several locations on the rotating shaft facing the inner surface of each curved plate piece forming the core. It consists of a cylinder body and a piston body that is pressed by a spring that is press-fitted into these cylinder bodies and presses the tip end face against the inner surface of each curved plate piece, and the stopper member is movable on the rotating shaft. 4. The propylene-based resin film winding device according to claim 3, wherein the propylene-based resin film winding device is configured by an end lid body that is disposed so as to be detachably engaged with both ends of the winding core. The urging mechanism for urging the winding core in the diameter-expanding direction includes a spring support member that is attached to several portions of the rotating shaft so as to face the inner surface of each curved plate piece forming the winding core, and these spring support members A tension spring that connects the outer circumferential surface of the winding plate and the inner circumferential surface of each curved plate piece forming the winding core, and constantly urges the winding core in the direction of diameter reduction, and is slidably disposed on the rotating shaft. The outer peripheral surface of the winding core is engaged with a tapered surface formed on the inner peripheral surface of the open end of the winding core in a wedge shape, and when the winding core moves in a direction approaching each other, the winding core is brought to the tensile force of the tension spring. The stopper member is composed of a short cylindrical body that is slidably fitted to the rotating shaft and presses against the outer end surfaces of the left and right wedge members. These short cylinders are pressed by a compression spring whose pressing force can be adjusted. Winding device of the propylene-based resin film according to claim 3,.

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