JP5202058B2 - Double-sided release film for fuel cells - Google Patents

Description

  The present invention relates to a release film, and more specifically, used to form a green sheet used as an electrolyte of a solid oxide fuel cell (hereinafter abbreviated as SOFC using an acronym for Solid Oxide Fuel Cell). It is related with the release film made.

  In recent years, the social need for countermeasures against global warming and environmental pollution has increased, and clean energy technology has been actively developed. As one of them, fuel cells are attracting attention.

  Fuel cells are regarded as promising as a clean power generation system that generates electricity by reacting hydrogen and oxygen in the air in an electrolyte and does not generate harmful gases. Among them, SOFC has a high operating temperature of about 500 ° C. or higher, and has an advantage that not only hydrogen gas but also natural gas and carbon monoxide can be used as a hydrogen source. Furthermore, since SOFC has a high operating temperature and high utility value of waste heat, the so-called cogeneration system has a high overall efficiency, compared to conventional power generation systems using gas combustion. A power generation system in which the amount of generated carbon dioxide is suppressed can be configured.

  SOFC is advantageous in that it is compact and highly durable because the electrolyte is solid, so there is no problem of electrolyte dissipation, the structure is relatively simple, and no reformer is required.

  A solid electrolyte used for SOFC is prepared by applying ceramic slurry composed of ceramic particles having ion conductivity (for example, zirconia-based particles), a binder, an additive, and the like, forming a sheet, and firing it. be able to.

  Conventionally, such a ceramic sheet is obtained by applying the ceramic slurry onto a release film based on a polyester film and molding the sheet, as in the production process of a ceramic multilayer capacitor, a ceramic substrate and the like. (For example, Patent Documents 1 and 2).

  On the other hand, since SOFC has a high operating temperature, the ceramic materials that can be used are limited. In addition, since it takes time to start up, studies have been made to lower the operating temperature. However, lowering the operating temperature of the fuel cell increases the internal resistance of the electrode / electrolyte. Therefore, reducing the thickness of the electrolyte to reduce resistance, searching for ceramic materials that have sufficient ionic conductivity even if the operating temperature is lowered, and catalysts Investigations such as searching for highly active electrode materials have been continued, and advanced ceramic members have been developed (for example, Patent Documents 3 to 6).

  With the advancement of ceramic materials as described above, the level of demand for ceramic sheet forming technology has increased, and the difficulty in the manufacturing process has also increased. For example, when thinning a ceramic sheet, it is required to control moderate wettability on the release surface so that the coating liquid does not repel even if the slurry is thinly coated. It is required to control moderate peelability so that the ceramic sheet does not adhere to the back polyester film surface after unwinding in the next step after storage.

  For these problems, a double-sided release film having a specific configuration is known, but the release film having these configurations was formed by coating a release layer on one side during the production of the release film. Later, because the release layer is applied and formed on the opposite surface, it is wound into a roll with the release surfaces in contact with each other. If the roll end face is uneven, or if there is a thickness distribution of the base film used for coating, it will be easier to meander, causing the roll end face not to be aligned, and rolls with slight impact during roll transport and transportation. There may be a problem that the vicinity of the core is wound like a bowl.

  On the other hand, in order to meet the requirement for reducing the resistance of the electrolyte at the low operating temperature described above, it is necessary to reduce the foreign matter mixed in at the time of forming the ceramic sheet. In particular, the incorporation of a silicone compound is particularly undesirable because it forms a glassy insulator after the firing step to increase the resistance of the electrolyte. Accordingly, there has been a demand for the release film that there is no transfer or contamination of the silicone compound from the release film to the ceramic slurry.

JP-A-10-29205 JP 2001-205607 A JP 2002-358976 A JP 2003-263994 A JP 2003-346816 A JP 2004-200125 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is that the SOFC green sheet can be prevented from adhering to the back surface after blocking (blocking) and breaking due to this, and the release film can be produced. It is difficult for irregularities on the roll end surface to occur, and even if there is a thickness distribution of the base film used for coating, irregularities on the end surface are unlikely to occur, and even if there is a slight impact during transportation and transportation of the release film roll, the winding core An object of the present invention is to provide a double-sided release film that does not easily wind in the form of a bowl.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problems can be easily solved by using a double-sided release film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is that a polyester film has a release layer mainly composed of a polyolefin or a long-chain alkyl compound on both sides, and the normal release force on one release layer surface (A surface) is 10 to 400 mN / cm, the normal release force on the other release layer surface (B surface) is 10 to 1000 mN / cm, and in X-ray photoelectron spectroscopy, the peak derived from the organosilicon compound is from any of the release layer surfaces Is not detected, and the static friction coefficient between the A side and the B side is 0.22 to 0.35.

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the release film in the present invention may have a single-layer structure or a laminated structure. For example, the polyester film may have a four-layer or a three-layer structure as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. It may be a multilayer having more than that, and is not particularly limited.

  The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyester includes polyethylene terephthalate (PET) and the like. On the other hand, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned. In any case, the polyester referred to in the present invention refers to a polyester that is usually 60 mol% or more, preferably 80 mol% or more of polyethylene terephthalate or the like which is an ethylene terephthalate unit.

  The average particle size of the particles used is preferably in the range of 0.1 to 5 μm, more preferably in the range of 0.5 to 5 μm. If the average particle size is less than 0.1 μm, the particles tend to aggregate and the dispersibility tends to be insufficient. On the other hand, if it exceeds 5 μm, the surface roughness of the film becomes too rough, When a release layer is provided in a subsequent process, problems may occur, and the quality of the obtained green sheet may be deteriorated.

  Furthermore, the particle content in the polyester is preferably in the range of 0.01 to 5% by weight, more preferably in the range of 0.01 to 3% by weight. When the particle content is less than 0.01% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the particle size of the particles is too large. As in the case, problems may occur in the step of providing the release layer, or the quality of the obtained green sheet may be deteriorated.

  The method for adding particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, the particles can be added at any stage for producing the polyester, but preferably, the polycondensation reaction may proceed after the esterification stage or after the transesterification reaction.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In the present invention, in the polyester film constituting the release film, in addition to the above particles, as long as it does not impair the gist of the present invention, conventionally known antioxidants, antistatic agents, Heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, fluorescent brighteners and the like can be added and used in combination.

  The thickness of the polyester film constituting the release film of the present invention is not particularly limited as long as it can be formed as a film, but is usually in the range of 25 to 250 μm, preferably 38, for use. It is in the range of ˜188 μm.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all.

  First, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, the extending | stretching temperature orthogonal to the extending | stretching direction of the 1st step is 70-170 degreeC normally, and a draw ratio is 3.0 to 7 times normally, Preferably it is 3.5 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  The simultaneous biaxial stretching method can also be adopted for the production of the polyester film in the present invention. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows: The area magnification is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above stretching method, a conventionally known stretching method such as a screw method, a pantograph method, a linear drive method, or the like can be employed.

  Further, a so-called coating stretching method (in-line coating) in which the film surface is treated during the stretching process of the polyester film can be applied. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, producing a film suitable as a polyester film. it can. This coating layer may be a release layer, or may be an adhesive layer for improving the adhesion of the release layer provided on this coating layer to the polyester film.

  By the way, as described above, in order to reduce the internal resistance of the fuel cell, it is necessary to reduce the thickness of the solid electrolyte. In this case, if the unevenness formed on the surface of the release film is large, the quality of the obtained solid electrolyte Will drop and problems will arise. For this purpose, specifically, the maximum height (Rmax) of the surface of the polyester film constituting the release film in the present invention is preferably 1.5 to 30 μm, more preferably 3 to 20 μm.

  Further, in the polyester film constituting the release film in the present invention, as a method for forming the film surface having the maximum height (Rmax), a particle kneading method, a particle coating method, an embossing method, a sand blasting method, an etching method are used. A method such as an electric discharge machining method can be used. In the present invention, any of the methods described above may be adopted, and there is no particular limitation.

  Next, formation of the release layer in the present invention will be described. That is, the normal state peeling force of the release surface (A surface) on which the ceramic green sheet is normally formed of the release film of the present invention is in the range of 10 to 400 mN / cm or more, preferably 20 to 200 mN. / Cm range. When the normal peel force exceeds 400 mN / cm, particularly when the green sheet is thin, the green sheet is difficult to peel off when the green sheet is peeled off, and breaks when it is forcibly peeled off. On the other hand, when it is less than 10 mN / cm, problems such as the green sheet being partially peeled off from the end of the carrier film during the process.

  On the other hand, the release surface formed on the back surface (B surface) of the A surface on which the ceramic green sheet is formed comes into contact with the green sheet after it dries. Is in the range of 10 to 1000 mN / cm, preferably in the range of 20 to 500 mN / cm.

  The static friction coefficient between the A surface and the B surface of the film of the present invention is in the range of 0.22 to 0.35. When the coefficient of static friction is less than 0.022, the film slips easily even with a weak force between the films, and the roll end face is uneven during the winding process, and the thickness distribution of the base film used for coating is If it exists, as a result of being easy to meander, there is a concern that the roll end faces are not aligned, and that the vicinity of the winding core is wound like a bowl due to a slight impact during the conveyance and transportation of the roll. On the other hand, if the coefficient of static friction exceeds 0.35, the film end position adjustment at the time of winding will be hindered and the roll end faces will not be aligned easily. Also, if the film end position is forcibly adjusted, scratches are likely to occur as a result of strong rubbing between the films. In addition, since the tightness does not easily occur during winding, when the accuracy of the device is poor, it is wound unevenly, and it cannot be relaxed, leaving an air layer between the films, so-called voids It is easy to become.

  The release layer constituting the release film in the present invention may be provided on the polyester film in the film production process such as the above-described coating stretching method (in-line coating), and is applied outside the system on the once produced film. So-called off-line coating may be employed, and any method may be employed. The coating stretching method (in-line coating) is not limited to the following, but for example, in sequential biaxial stretching, the first stage of stretching may be completed and the coating treatment may be performed before the second stage of stretching. it can. When a release layer is provided on a polyester film by a coating and stretching method, the film can be applied simultaneously with stretching, and the thickness of the release layer can be reduced according to the stretching ratio. Can be manufactured.

  Moreover, it is preferable that the release layer constituting the A surface and the B surface in the present invention mainly contains a polyolefin or a long-chain alkyl compound in order to improve the releasability. The polyolefin is not particularly limited, and examples thereof include polyethylene, polypropylene, polybutene, polyhexene, and copolymers thereof. A homopolymer with other components and having a slightly reduced crystallinity is more preferable than a homopolymer. The long-chain alkyl compound is a compound having a linear or branched alkyl group having 6 or more carbon atoms, particularly preferably 8 or more. Specific examples include, but are not limited to, long-chain alkyl group-containing polyvinyl resins, long-chain alkyl group-containing acrylic resins, long-chain alkyl group-containing polyester resins, long-chain alkyl group-containing amine compounds, long-chain alkyl groups. And an ether compound, a long-chain alkyl group-containing quaternary ammonium salt, and the like. In view of contamination, a polymer compound is preferable. These are more preferably crosslinked because they are required to withstand processing at about 100 ° C. to 180 ° C. Examples of the method for forming a crosslinked structure of a polyolefin or a long-chain alkyl compound include a method in which a reactivity is imparted to a part of the polyolefin or the long-chain alkyl and this is crosslinked with a polyfunctional compound.

  In the present invention, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like can be used as a method for providing a release layer on the polyester film. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

In the present invention, the curing conditions for forming the release layer on the polyester film are not particularly limited, and when providing the release layer by off-line coating, usually at 120 to 200 ° C. for 3 to 40 seconds, The heat treatment is preferably performed at 100 to 180 ° C. for 3 to 40 seconds as a guide. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. In addition, a conventionally well-known apparatus and an energy source can be used as an energy source for hardening by active energy ray irradiation. The coating amount of the release layer from the viewpoint of coating property, usually 0.005~1g / ^{m 2,} preferably in the range from 0.005 to 0.5 / ^{m 2.} If the coating amount is less than 0.005 g / m ² , the coating property may be less stable and it may be difficult to obtain a uniform coating film. On the other hand, when the coating is thicker than 1 g / m ² , the coating layer adhesion and curability of the release layer itself may be lowered.

  The residual adhesive rate of the A side and the B side of the double-sided release film of the present invention is preferably 80% or more. More preferably, both are 85% or more. If the residual adhesion rate is less than 80%, there will be more migration of contaminants to the surface of the counterpart green sheet that is in contact with the release surface of the release film. However, it remains as an oxide or the like after firing, and there is a concern that the normal electrode reaction may be inhibited.

  According to the present invention, a film suitable for forming a green sheet used for an electrolyte of a solid oxide fuel cell can be provided, and the industrial value of the present invention is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measuring method used in the present invention is as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of a sample was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measured at 30 ° C.

(2) Measurement of average particle size (d50: μm) 50% integrated (weight basis) in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) The value was defined as the average particle size.

(3) Measurement of maximum height (Rmax) of polyester film Only a reference length (2.5 mm) was extracted from a cross-sectional curve obtained by a surface roughness measuring machine (SE-3F) manufactured by Kosaka Laboratory Ltd. When the extracted part is sandwiched by two straight lines parallel to the average line of the part (hereinafter referred to as the extracted part), the distance between the two straight lines is measured in the direction of the vertical magnification of the cross-sectional curve, and the value is measured in units of micrometers (μm) The maximum height of the extracted part is represented by. The maximum height was expressed as an average value of the maximum heights of the extracted portions obtained from 10 cross-sectional curves obtained from the sample film surface. The radius of the stylus used at this time was 2.0 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

(4) Evaluation of peel strength (F) of release film One side of a double-sided pressure-sensitive adhesive tape (Nitto Denko “No. 502”) was attached to the release layer of the measurement sample, cut into a size of 50 mm × 300 mm, and room temperature The peel force after standing for 1 hour was measured. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under the condition of a tensile speed of 300 mm / min.

(5) Measurement of static friction coefficient (μs) Two test pieces are stacked and one is fixed to a flat metal plate, the other is connected to a load meter, a weight is placed on the test piece, and 20 mm parallel to the test piece. The load Fs when moving at a speed of / min and starting to move was calculated and calculated according to the following formula (according to ASTM D1894-73).

μs = Fs / weight weight (6) Green sheet peelability evaluation A ceramic slurry having the following composition was coated on the A side of the release film so that the coating amount (after drying) was 50 μm, and at 120 ° C. A green sheet was obtained by drying.
The peelability when the obtained green sheet was peeled was determined according to the following criteria.
<< Ceramic slurry composition >>
Ceramic powder (zirconia particles) 100 parts Binder (polyvinyl butyral resin) 20 parts Plasticizer (dioctyl phthalate) 1 part Toluene / MEK (1: 1) mixed solvent 20 parts

<Criteria>
○: Can be peeled off smoothly (no problem in practical use)
×: Difficult to peel (practically problematic level)

(7) Evaluation of anti-blocking of the green sheet on the back side of the film The green sheet obtained in the above item (6) was laminated so that the B surface of the release film coated with the green sheet was in contact with the green sheet. Pressing was performed at a temperature of 40 ° C., a humidity of 80% RH, and a load of 10 kg / cm ² for 20 hours to evaluate blocking resistance. The judgment criteria are as follows.
<Criteria>
○: The B side of the release film can be peeled off by hand (a level that causes no problem in practice)
× It is difficult to peel the B side of the release film by hand (practically problematic levels such as easy cracking of the sheet during handling)

(8) Evaluation of anti-winding resistance A roll-shaped film in which a release film having a width of 1100 mm is wound around a 3-inch paper core, 500 m in length, is placed on a horizontal rubber stand so that the winding core is parallel to the floor. In this state, a metal rod for pulling the winding core is passed through the winding core and fixed to the end of the winding core via a metal fitting, and a spring with a maximum measurement load of 10 kg is placed on the opposite side to the fixed side. In a state where only the cores are connected, a slow tensile load is manually applied to the core, and whether or not the core moves is visually evaluated until only the spring shows a 5 kg weight.
<Criteria>
○: The core does not move at all (a level that does not cause any practical problems)
×: Winding core moves (practically problematic level)

(9) Detection of organosilicon compound The silicone compound was quantified by X-ray photoelectron spectroscopy using Shimadzu "ESCA-1000". That is, with an output of 8 kV and 300 mA, an MgKα ray is used as a radiation source, and an area of about 1 mm in diameter is measured at a wide scan in a measurement mode “Small” at 100 locations, and Si near 102.3 eV caused by an organosilicon compound is measured. (2p) A peak is detected. When it overlaps with the Si (2p) peak near 103.0 eV due to the inorganic silicon compound, peak separation is appropriately performed. The silicon-derived silicon atom abundance ratio with respect to carbon atoms was calculated with C (1S) = 1.0 and Si (2S) = 0.86.

<Manufacture of polyester>
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, the temperature is raised by heating, methanol is distilled off, transesterification is performed, and 4 hours are required from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of ethyl acid phosphate, 0.03 part of antimony trioxide and 0.06 part of silica particles having an average particle diameter of 2.5 μm were added, and then the temperature reached 280 ° C. and the pressure reached 15 mmHg in 100 minutes. After that, the pressure was gradually reduced after that to finally reach 0.3 mmHg. After 4 hours, the system was returned to normal pressure to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65.

Examples of compounds constituting the coating stretch method (in-line coating) release layer are as follows.
(Example compounds)
Long chain alkyl compound A:
To a four-necked flask, 200 parts of xylene and 600 parts of otadecyl isocyanate were added and heated with stirring. From the time when xylene began to reflux, 100 parts of polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 88 mol% was added in small portions over a period of about 2 hours.
After the addition of polyvinyl alcohol, the reaction was completed by further refluxing for 2 hours.
When the reaction mixture was cooled to about 80 ° C. and added to methanol, the reaction product was precipitated as a white precipitate. This precipitate was filtered off, added with 140 parts of xylene, and heated to dissolve completely. After repeating the operation of adding methanol again to precipitate several times, the precipitate was washed with methanol and dried and ground.

<Manufacture of polyester film F1>
3 parts of silicon dioxide particles having an average particle size of 3.5 μm, polyethylene terephthalate having an intrinsic viscosity of 0.65 are dried at 180 ° C. for 4 hours in an inert gas atmosphere, melted at 290 ° C. by a melt extruder, And then solidified by cooling on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched sheet. The obtained sheet was stretched 3.5 times in the longitudinal direction at 85 ° C., and then the coating amount of the compound A as an aqueous solution on the longitudinally stretched film was dried to be 0.02 g / m ^2. After coating, the film was led to a tenter and stretched in the transverse direction by 3.7 times at 100 ° C. and then heat-set at 230 ° C. to obtain a polyester film F1 (Rmax = 4.5 μm) having a thickness of 50 μm. It was.

<Manufacture of polyester film F2>
In the production of the polyester film F1, a polyester film F2 (Rmax = 4.5 μm) having a thickness of 50 μm was obtained in the same manner except that the compound A was not applied.

Examples of coating solutions when the release layer is formed by off-line coating are as follows.
(Example of coating solution)
Metallocene polyethylene (kernel KS340T; manufactured by Nippon Polyethylene), ethylene / propylene rubber (EP02P; manufactured by JSR), low molecular weight polyolefin-based polyol (polytail HA; manufactured by Mitsubishi Chemical), isocyanate (Mitec NY718A; manufactured by Mitsubishi Chemical) and amine catalyst ( 1,4-diazabicyclo- [2.2.2] -octane; manufactured by Wako Pure Chemical) and toluene (special grade manufactured by Wako Pure Chemical) at a weight ratio of 792: 792: 16: 10: 16: 98374, respectively. Mixing was performed to prepare coating solution B.

Example 1:
On the surface (B surface) opposite to the surface (A surface) on which the inline coating of the polyester film F1 obtained above is applied, the coating liquid B is applied to the coating liquid B using a Mayer bar # 6 with a clean coater of class 100. The film was coated on the B side and heat treated at 130 ° C. for 1 minute to obtain a double-sided release film having a normal peel strength of A side of 255 mN / cm and a B side of 31 mN / cm.

Example 2:
On the both surfaces of the polyester film F2 obtained above, the coating liquid B was applied to both surfaces using a Mayer bar # 6 with a clean coater of class 100 and subjected to heat treatment at 130 ° C. for 1 minute. A double-sided release film having a normal peel strength of 31 mN / cm and a B surface of 31 mN / cm was obtained.

Comparative Example 1:
A release layer made of silicone resin C1 was provided on both surfaces of the polyester film F2 obtained above so that the coating amount was 0.1 g / m ² (after drying). A double-sided release film having a normal peeling force of A side of 20 mN / cm and a B side of 20 mN / cm was obtained.
<< Releasing agent composition >> C1
Curable silicone resin (manufactured by Shin-Etsu Chemical: X62-5039) 100 parts Curing agent (manufactured by Shin-Etsu Chemical: CAT-PL-50T) 5 parts The above mold release agent is mixed with toluene / methyl ethyl ketone mixed solvent (mixing ratio = 1: 1). Dilution was performed to obtain a coating solution having a solid content concentration of 2% by weight.

Comparative Example 2:
In Example 2, normal peeling was performed in the same manner as in Example 2 except that the silicone resin C1 was used instead of the A-side polyolefin so that the coating amount was 0.1 g / m 2 (after drying). A double-sided release film having a force of 20 mN / cm on the A side and 31 mN / cm on the B side was obtained.

Comparative Example 3:
The polyester film F2 obtained above was evaluated.
The characteristics of each film obtained in the above Examples and Comparative Examples are shown in Table 1 below.

  The film of the present invention can be suitably used for forming a green sheet used as an SOFC electrolyte, for example.

Claims (1)

The polyester film has a release layer mainly composed of a polyolefin or a long-chain alkyl compound on both surfaces, and the normal release force on one release layer surface (A surface) is 10 to 400 mN / cm, and the other release layer The normal state peeling force of the mold layer surface (B surface) is 10 to 1000 mN / cm, and in X-ray photoelectron spectroscopy, no peak derived from the organosilicon compound is detected from any of the release layer surfaces, A double-sided release film for a fuel cell, wherein the coefficient of static friction with the B surface is 0.22 to 0.35.