KR101845845B1 - Apparatus of manufacturing battery separator - Google Patents

Abstract

A manufacturing apparatus for a separator for a battery, which is manufactured by a dry process and improves crystallinity and air permeability, enhances mechanical strength and electrolyte permeability, lowers heat shrinkage, and prevents fracture in a stretching process. An apparatus for producing a separator by extruding a polymer resin to form an unstretched sheet, thermally molding an unstretched sheet, and then subjecting the sheet to a low-temperature and high-temperature stretching to form a separator, the apparatus being disposed between the thermoforming and the low- And an activation roll for heat-treating the unstretched sheet at an activation temperature to prevent heat shrinkage of the unstretched sheet to remove residual stress of the new sheet.

Description

[0001] Apparatus of manufacturing battery separator [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a separator for a battery, and more particularly to an apparatus for dry-separating a separator used in a battery using an activation roll.

The separator for a battery should have generally required physical properties such as mechanical strength and permeability of an electrolyte, and preferably has a low heat shrinkage rate and a high porosity at a high temperature. The battery separator may be manufactured by various processes, and the characteristics of the separator may vary depending on the process. The process for producing the separator can be roughly divided into a dry process and a wet process. Since the wet process uses an extraction solvent, it is not environmentally friendly, and the production process is complicated, resulting in low price competitiveness. In the dry process, an inorganic material is added or a crystal structure is controlled to produce a separator. In the method of adding an inorganic material, the quality is unstable due to the uneven porosity and low strength. Therefore, .

In the dry process for controlling the crystal structure, a molten polymer resin is extruded to prepare an unstretched sheet, the crystal structure is controlled through thermoforming, and pores are formed by stretching to produce a separator. U.S. Patent No. 5,013,439 describes in detail the process of forming pores by low-temperature stretching and high-temperature stretching. The membrane prepared by the dry process does not use the extraction solvent and is environmentally friendly, and the production process is simple, and it has high price competitiveness.

On the other hand, the conventional separation membrane is subjected to a stretching process after cooling to a temperature near room temperature without any additional process after thermoforming. When the separator which has been thermoformed at a high temperature is cooled to a room temperature, the crystallization of the unstretched sheet does not occur properly due to rapid cooling, and the crystallinity and pore uniformity of the separator deteriorate. If the crystallinity and pore uniformity are lowered, the mechanical strength, electrolyte permeability and air permeability of the separator are lowered. In addition, if quenching occurs, the sheet is hardened because it does not have a sufficient time to stabilize the microstructure, so that the crystal structure in the polymer is unstable and it is difficult to control the physical properties. In addition, since the non-stretched sheet crystallized through quenching has a hard surface, breakage often occurs in the subsequent low-temperature stretching process. Thereby, it is necessary to control the cooling conditions of the non-oriented sheet after thermoforming to promote sufficient crystal growth, and to stabilize the microstructure in the sheet to improve its physical properties.

A problem to be solved by the present invention is to provide an apparatus for manufacturing a separator for a battery, which is manufactured by a dry process and improved in crystallinity and pore uniformity, has high air permeability, high electrolyte permeability, high pore uniformity, I have to.

An apparatus for producing a battery separator for solving the problems of the present invention is an apparatus for producing a separator by extruding a polymer resin to form an unstretched sheet, thermally molding the unstretched sheet, and then subjecting the sheet to stretching at a low temperature and a high temperature, And an activation roll disposed between the thermoforming and the low temperature stretching process and heat-treating the unstretched sheet at a polymer activation temperature to increase the degree of crystallization of the unstretched sheet and to remove residual stress.

In the apparatus of the present invention, the diameter of the activation roll may be set in consideration of the cross-sectional area in which the non-extension sheet contacts the activation roll. The diameter of the activation roll is preferably 800 mm to 1,500 mm.

In the preferred apparatus of the present invention, the activation roll may be adhered with a thermal uniform layer for uniformly supplying heat to the unstretched sheet. The heat uniform layer may be any one selected from a rubber layer made of rubber or a fabric composed of polymer fibers or a composite thereof. The thermal uniform layer may be a felt formed by mixing the rubber and the polymer fibers in powder form. And a thermal conductive layer between the thermal uniform layer and the activation roll. The thermally conductive layer may be formed of any one selected from a thermally conductive metal, an alloy of the metal, and a material in which an insulating binder is mixed with the metal and the alloy.

According to the apparatus for producing a battery separator of the present invention, the non-oriented sheet is activated after thermoforming to improve the crystallinity and the porosity. Accordingly, the permeability of the separator, the uniformity of the pores, and the electrolyte permeability can be increased, and fracture during stretching can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart showing a method for producing a battery separator according to the present invention;
FIG. 2 is a schematic view for explaining an activation device applied to the activation process according to the present invention.
FIG. 3 is a view showing a state in which a thermally uniform layer is added in FIG. 2. FIG.
4 is a graph comparing the air permeability according to the activation time according to the conventional comparative example and the embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

An embodiment of the present invention proposes an apparatus for manufacturing a separator for a battery which improves crystallinity and porosity by activating an unstretched sheet after thermoforming. That is, it is possible to improve the crystallinity and the porosity to improve the permeability and the permeability of the electrolyte, and to prevent the breakage from occurring in the stretching process. For this purpose, the separation membrane production process including the activation process will be described in detail, and the physical properties of the separation membrane produced by the above process will be described in detail. The separator of the present invention is produced by a dry process. That is, the present invention is not applied to an extraction solvent, but may be applied to a particle drawing process in which pore-forming particles are added as the case may be.

1 is a flowchart showing a method of manufacturing a separator for a battery according to an embodiment of the present invention.

Referring to FIG. 1, the separator of the present invention firstly extrudes a polymer resin to produce an unstretched sheet (S10). At this time, the polymer resin is preferably semicrystalline, and examples thereof include polyolefins, polyfluorocarbons, polyamides, polyesters, polyacetals, polysulfides, polyvinyl alcohols, copolymers thereof, and combinations thereof And may be a polymer compound selected from the group consisting of The polymer resin is preferably a polyolefin resin. Examples of the polyolefin resin include homopolymers of olefins such as polypropylene, high-density polyethylene, low-density polyethylene, low-density polyethylene, polybutene, and polystyrene, ethylene-propylene copolymers, Copolymers of olefins such as propylene-butene copolymer, and mixtures thereof.

When the polymer resin is extruded, various kinds of additives such as a reinforcing material, a filler, an antioxidant, a surfactant, a neutralizer, a heat stabilizer, a weather stabilizer, an antistatic agent, a lubricant, a slip agent, Additives may be added. The additive is not particularly limited as long as it is a material known in the art. It is more preferable to add an antioxidant to such additive for ensuring long-term heat resistance and oxidation stability.

The extrusion method for the unstretched sheet is not particularly limited, but a single screw or twin screw extruder and a T-shaped or annular die can be used. The molten polymer resin is discharged through the die and is made of an unstretched sheet by a casting roll. On the other hand, air can be injected into the casting roll by using an air knife or an air ring in order to adjust the temperature of the discharged resin or to improve the state of the separation membrane in a subsequent process. It is preferred that the lamellar of the unstretched sheet is oriented perpendicular to the longitudinal direction (machine direction), and the lamellar lamination is made along the longitudinal direction. The non-oriented sheet of the present invention generally has a crystallinity of at least 20%, preferably at least 30%, and most preferably at least 50%.

Thereafter, the unstretched sheet is thermoformed (S12). The thermoforming promotes crystallization throughout the sheet, increases the size of the crystalline and removes defects. The thermoforming is performed at a temperature of about 5 ° C to 50 ° C lower than the melting point of the polymeric resin for several seconds to several hours (for example, 5 seconds to 24 hours, more preferably about 30 seconds to 2 hours). For example, an unoriented sheet made of polypropylene is thermoformed at a temperature in the range of about 100 ° C to 60 ° C. The thermoforming is not particularly limited, but heat can be applied to the unstretched sheet through, for example, an oven in which a tropical stream occurs, contact with a heating roll, hot air in a tenter, or an IR heater .

Next, the activation process of the thermoformed unstretched sheet according to the embodiment of the present invention is performed (S14). It is preferable that the temperature of the activation step is 90 ° C to 110 ° C, preferably 95 ° C to 105 ° C. The activation process is carried out by the activation roll, and the activation temperature is the temperature at which the activation roll is applied to the unstretched sheet. If the activation temperature is lower than 80 ° C, it is difficult to obtain the activation effect according to the embodiment of the present invention. If the activation temperature is higher than 110 ° C, crystallization of the non-oriented sheet occurs excessively. The activation temperature may vary depending on the temperature and time in the thermoforming process, the material of the unstretched sheet, and the like.

Subsequently, the stretched thermoformed sheet is subjected to low-temperature stretching to form a crack on the sheet surface (S16). The low temperature stretching process can be stretched in the machine direction using a stretching roll. The temperature of the low-temperature stretching process can be set to a temperature at which cracks can be formed in the amorphous region depending on the kind of the semi-crystalline polymer compound that is a component of the non-stretched sheet. For example, between (Tg-20 deg. C) and (Tg + 70 deg. C) based on the glass transition temperature (Tg) of the polymer compound used is appropriate. (Tg-20 DEG C), there is a high possibility of breakage during low-temperature stretching, and uniform crack formation is difficult. (Tg + 70 deg. C), cracks formed again are recovered by the thermal action of the polymer.

In the low temperature stretching process, the elongation is preferably 10 to 100%. When the elongation is 10% or less, cracks are not sufficiently formed in the amorphous region, and the air permeability after high-temperature stretching is lowered. If it is 100% or more, breakage is caused in the low temperature stretching process, and the production efficiency is lowered. On the other hand, the thermoformed sheet is in a hard state because of its high crystallinity. Therefore, since the elongation is low at low temperatures, it is difficult to elongate at a high ratio unless heat is applied. For this purpose, in order to stretch at a high ratio, the following high-temperature stretching is required.

Next, the low-temperature stretched film is subjected to high-temperature stretching to form a separator (S18). The temperature of the high-temperature stretching process is suitably between (Tm-40 占 폚) and (Tm-10 占 폚) on the basis of the melting temperature (Tm). (Tm-40 占 폚), there is a high possibility that the film breaks in the process of expanding the pores at the crack portion of the low-temperature stretched film. Cracks formed by low-temperature stretching are similar to some defects in the polymer. If a force is applied in a state in which sufficient heat is not applied, cracks are generated around the cracks. (Tm-10 ° C), the pores are closed because of the high fluidity of the polymer. The high-temperature stretching method is variously known, but it is preferable to stretch to 100 to 500% by longitudinal stretching. In some cases, transverse stretching can also be carried out.

It is preferable that the separator according to the embodiment of the present invention is stretched by about 150 to 250% as compared with an unoriented sheet subjected to thermoforming. The separation membrane subjected to the high temperature stretching process relaxes the heat applied to the separation membrane through heat fixation and stabilizes the microstructure (S20). The heat-set separation membrane is wound by a take-up roll (S22).

2 is a schematic view for explaining an activation device applied to an activation process according to an embodiment of the present invention. FIG. 3 is a view showing a state in which a thermally uniform layer is added in FIG. 2. FIG.

2 and 3, the non-extruded sheet 30 having passed through the thermoforming roll 20, for example in the thermoforming process, is directed to the cooling roll 22 in the cooling process via the activating region 10. At this time, the unstretched sheet 30 is put into the activation process by two methods. One being activated by contact with the activation roll 12, and the other being activated by contact with the thermal uniform layer 18. The activation process of the present invention can be carried out in any one of the above two ways. However, it is preferable that the temperature of the activation process performed by the activation roll 12 or the heat uniform layer 18 is 90 ° C to 110 ° C, preferably 95 ° C to 105 ° C. The activation temperature refers to the temperature applied to the non-smear sheet 30 by the activation roll 12 or the heat uniform layer 18. [ Accordingly, the activation temperature is a characteristic that applies only to the embodiment of the present invention.

The activation roll 12 is preferably in the form of a cylinder, and a thermal uniform layer 18 according to an embodiment of the present invention is formed around the activation roll 12. It is preferred that the temperature of the activation roll 12 be maintained at a temperature of 100 ° C to 150 ° C, and the thermal uniformity layer 18 satisfies the above activation temperature. For this purpose, the fruit passage 14 can be fed with fruit. The activation roll 12 may use a metal such as stainless steel which is resistant to thermal shock and corrosion. The unstretched sheet 30 moves while contacting the thermal uniform layer 18 of the activation roll 12. In the course of heat treatment of the unstretched sheet 30, the activating roll 12 is preferably rotated in the direction in which the unstretched sheet 30 is fed.

The undrawn sheet 30 is subjected to an activation process, and crystallization is promoted inside. The crystallized unoriented sheet 30 is subsequently subjected to a drawing process, a heat setting process, and the like, and pores are formed in the region between the crystals. The amorphous part between crystals has a relatively weak bonding force. Generally, the crystallized unstretched sheet 30 has a higher strength and hardness than the amorphous sheet. So that breakage often occurs in the subsequent stretching process. If the heat treatment is performed at the activation temperature as in the embodiment of the present invention, rapid cooling is prevented, microstructure is stabilized, and latent heat is generated in the sheet, thereby preventing breakage in the stretching process.

On the other hand, the diameter D of the activation roll 12 can be set in consideration of the cross-sectional area S at which the non-extension sheet 30 contacts the activation roll 12. [ As the diameter D increases, the cross-sectional area S also increases. The diameter D of the activation roll 12 according to the embodiment of the present invention is preferably 800 mm to 1,500 mm. If the diameter D is out of the above range, it is difficult to adjust the cross-sectional area S appropriately. Particularly, when the diameter D is smaller than 800 mm, the cross-sectional area S contacting with the non-oriented sheet 30 becomes small, so that the time required for promoting crystallization and stabilizing microstructure is sufficiently shortened.

The heat uniform layer 18 according to the embodiment of the present invention absorbs the heat generated in the activation roll 12 and uniformly supplies the heat to the non-stretch sheet 30. If the non-stretch sheet 30 directly contacts the activation roll 12 without the thermally uniform layer 18, the heat may not be uniformly transmitted to the non-stretch sheet 30. The thermal uniform layer 18 is added to prevent non-uniform heat transfer. At this time, the diameter Da and the cross-sectional area S of the thermal uniform layer 18 are as described in the activation roll 12.

The heat uniform layer 18 is made of a material which is easy to contact with the unstretched sheet 30 and which absorbs heat without leaving defects on the surface. The heat uniform layer 18 according to the embodiment of the present invention is preferably a rubber layer made of rubber to which heat absorbing material is added or a fabric made of polymer fibers or a composite thereof. Since the rubber material has a predetermined tackiness, the non-smear sheet 30 is easily contacted with the thermal uniform layer 18. It is possible to prevent the unstretched sheet 30 from being disturbed by the environment outside the activation roll 12 when the unstretched sheet 30 comes into contact with the thermally uniform layer 18 having adhesive property. Here, the disturbance is that the unstretched sheet 30 is shaken by the flow of the fluid around the activating roll 12, or the unstretched sheet 30 is not desired by the thermoforming roll 20 or the cooling roll 22 A phenomenon that is dragged away.

The rubber may be at least one selected from the group consisting of fluorine rubber including Teflon, acrylic rubber, polyurethane rubber, polyamide rubber, natural rubber, polyisobutylene rubber, polyisoprene rubber, chloroprene rubber, butyl rubber, nitrile butyl rubber, styrene- Butadiene rubber, styrene-ethylene-butylene-styrene rubber, styrene-isoprene-propylene-styrene rubber, silicone rubber, chlorosulfonated polyethylene rubber, or any one selected from the group consisting of styrene-butadiene-styrene rubber, styrene- Or a mixture thereof. The fabric is woven of polymer fibers that do not undergo thermal denaturation at the activation temperature.

Preferably, the thermally uniform layer 18 is a felt formed by mixing rubber and polymer fibers in powder form. The felt has a self-adhesive force. The self-adhesive force is a property of attaching itself without bubbles between the unstretched sheet 30 and the thermal uniform layer 18 even if the unstretched sheet 30 is put on the thermal uniform layer 18. [ At this time, the self-adhesive force is suitably about 0.1 gf / 25 mm to 300 gf / 25 mm, more preferably 0.2 gf / 25 mm to 50 gf / 25 mm. In the embodiment of the present invention, the thickness of the thermal homogeneous layer 18 is preferably 100 占 퐉 to 10,000 占 퐉. If the thickness of the heat uniform layer 18 is less than 100 占 퐉, the effect of uniformly transmitting heat to the non-stretchable sheet 30 is insufficient. If the thickness is greater than 10,000 占 퐉, the cost of forming the thermal uniform layer 18 increases and it is thicker than necessary to realize the desired properties in the present invention. If the thickness is large, it takes a long time to secure a desired heat in the thermal uniform layer 18. [

Optionally, embodiments of the present invention may further form a thermally conductive layer 16 between the thermal uniform layer 18 and the activation roll 12. The thermally conductive layer 16 provides a path through which heat can be easily transferred from the activation roll 12 to the thermal uniform layer 18. [ The heat conductive layer 16 allows the heat to be more effectively transferred in the thickness direction and the machine direction. The heat conduction layer 16 allows the absorbed heat to diffuse and distribute uniformly, so that the heat is easily transferred to the heat conduction layer 16. The thermally conductive layer 16 prevents the localized areas of the activation roll 12 and the thermal uniform layer 18 from being heated to help the heat to be transferred uniformly. The heat conduction layer 16 is preferably made of a metal material having a good thermal conductivity, and can be formed in a film form or through deposition.

The heat conduction layer 16 may be made of any one selected from a thermally conductive metal such as gold, silver, copper, aluminum, or nickel, an alloy of the metal, or a material in which an insulating binder is mixed with the metal and the alloy. The binder may be any one or a combination of silicon polymer, epoxy, polyimide, polyethylene, polypropylene, polyphenylene oxide, polysulfone, silicon dioxide, aluminum oxide, zirconia and other metal oxides. The thickness of the heat conduction layer 16 is preferably from 100 mu m to 1,000 mu m. If the thickness of the heat conduction layer 16 is less than 100 mu m, the heat conduction effect does not occur properly. If the thickness is larger than 1,000 占 퐉, the cost of forming the heat conduction layer 16 rises excessively and is thicker than necessary to realize the desired properties in the present invention.

In order to explain the physical properties of the separator of the present invention in detail, the following examples are presented. However, the present invention is not particularly limited to the following examples. In addition, the air permeability of the separation membrane shown in Examples and Comparative Examples shows the values measured by the following methods.

- Measuring instrument: Gurley Type Densometer Model G-B2C from Toyoseiki of Japan.

- Measurement method: Measured in seconds (sec) / 100 ml, in which 100 ml passes at a temperature of 23 ± 2 ° C and a humidity of 50 ± 5% RH in accordance with JIS P8117.

<Examples>

 80% by weight of polyethylene (Homo PP) and 20% by weight of other additives. After thermoforming at a temperature of 165 DEG C for 3 minutes, the heat-treated non-stretched sheet was heat-treated at 100 DEG C in an activation roll. Thereafter, 400% stretching was carried out at a low temperature and a high temperature stretching step, and heat setting was carried out at 155 DEG C for one minute. The air permeability of the open membrane-bound separator was measured.

<Comparative Example>

80% by weight of polyethylene (Homo PP) and 20% by weight of other additives. After the sheet was thermally formed at a temperature of 165 캜 for 3 minutes, the sheet was immediately cooled (quenched), stretched at 400% in a low temperature and high temperature stretching process, and heat set at 155 캜 for 1 minute. The air permeability of the open membrane-bound separator was measured.

4 is a graph comparing the air permeability according to the activation time according to the conventional comparative example and the embodiment of the present invention.

4, when the activation time at 25 ° C was 20 seconds, 40 seconds, 60 seconds, and 90 seconds, the conventional separator had air permeability of 837 seconds, 912 seconds, 905 seconds, and 942 seconds, respectively. As the activation time increased, the air permeability increased. In other words, activation at 25 ° C not only improves air permeability, but also adversely affects air permeability as time increases. In contrast, when the activation time was 20 seconds, 40 seconds, 60 seconds, and 90 seconds, the air permeability of the membrane according to the present invention was 681 seconds, 648 seconds, 499 seconds, and 393 seconds, respectively. As the activation time increased, the air permeability became shorter and shorter. That is, activation at 100 ° C improves the air permeability, and as the activation time increases, the air permeability becomes better.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the spirit and scope of the invention. It is possible.

10; Activation region 12; Activation roll
14; Fruit passage 16; Heat conduction layer
18; A thermal uniform layer 20; Thermoforming roll
22; Cooling roll

Claims (8)

An apparatus for producing a separator by extruding a polymer resin to form an unstretched sheet, thermoforming the unstretched sheet, and subjecting the sheet to stretching at a low temperature and a high temperature,
And an activation roll disposed between the thermoforming and the low temperature stretching process for heat treating the unstretched sheet at a polymer activation temperature to increase the degree of crystallization of the unstretched sheet and to remove residual stress,
Wherein the activation roll is attached with a heat uniform layer for uniformly supplying heat absorbed from the activation roll to the non-oriented sheet, the thermal uniform layer being easy to contact with the non-oriented sheet, A rubber layer made of rubber which does not leave defects, or a fabric composed of polymer fibers, or a composite thereof,
Wherein the activating roll includes a heat transfer path for supplying heat to the inside of the activation roll. The apparatus for manufacturing a separator for a battery according to claim 1, wherein the diameter of the activation roll is set in consideration of a cross-sectional area of the non-extension sheet contacting the activation roll. The apparatus for manufacturing a separator for a battery according to claim 2, wherein the diameter of the activation roll is 800 mm to 1,500 mm. delete delete The apparatus for manufacturing a battery separator according to claim 1, wherein the thermal uniform layer is a felt formed by mixing the rubber and the polymer fibers in a powder form. The apparatus for manufacturing a separator for a battery according to claim 1, further comprising a thermal conductive layer between the thermal uniform layer and the activation roll. The apparatus for manufacturing a battery separator according to claim 7, wherein the thermally conductive layer is made of any one selected from a thermally conductive metal, an alloy of the metal, or a material in which an insulating binder is mixed with the metal and the alloy.

Images