JP2006150812A - Release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a release film which is suitable for the cast molding of a sheet-like polymer structure, such as an electrolyte membrane, and which simultaneously satisfies that it is non-contaminating, inexpensive and excellent in heat resistance. <P>SOLUTION: The release film makes a polyester film its major structure. Peaks derived from organosilicon compounds are not detected on both the surfaces by X-ray photoelectron spectroscopic measurement. At least one surface is mainly composed of polyolefin, and the post-heating peeling strength of the surface is ≤80 mN/cm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a release film suitably used for producing an electrolyte membrane used in a fuel cell or the like.

  In recent years, fuel cells have attracted attention as clean energy sources that do not generate carbon dioxide, nitrogen oxides, and the like from the viewpoint of reducing environmental burden. In particular, solid polymer fuel cells, in which the ion exchange membrane, which can be said to be the heart, is a polymer electrolyte such as perfluorosulfonic acid resin, are being actively developed because they are easy to miniaturize and operate at relatively low temperatures. Yes.

Electrolyte membranes made of this polymer electrolyte, especially electrode membranes in which platinum catalyst-carrying carbon and the like are dispersed in the electrolyte, are formed in a paste-like or ink-like form with a solvent in the formation. It is often formed by casting on a material film. As a release film used here, for example, as described in Patent Document 1, (1) a silicone-coated polyester film, (2) a stretched polypropylene film, (3) a fluororesin film, (4) Examples include a polyester film laminated with a fluororesin. However, the silicone used as a release agent has a risk of contamination, and the fluororesin is generally expensive. Therefore, either a single substance, a laminate of this on another substrate, or a coating of this on another substrate can be used. In any case, the release film as a consumer material has a cost limitation, and is not suitable for the cost reduction of the electrolyte membrane that will be promoted in the future. Polyolefins such as polypropylene or polymers having long-chain alkyl side chains are inexpensive and have a certain releasability, but they are not necessarily releasable. There are restrictions on use.
JP 2003-285396 A

  The present invention has been made in view of the above circumstances, and its solution is a mold release suitable for cast molding of a sheet-like polymer structure such as an electrolyte membrane, which simultaneously satisfies non-contamination, low cost, and excellent heat resistance. To provide a film.

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

  That is, the gist of the present invention is a film having a polyester film as a main structure, and a peak derived from an organosilicon compound is not detected on any surface by X-ray photoelectron spectroscopy measurement, and at least one surface is The release film is composed mainly of polyolefin and has a heat peeling force of 80 mN / cm or less on the surface.

Hereinafter, the present invention will be described in detail.
In the release film of the present invention, a stretched film comprising a base material made of polyester, particularly an aromatic polyester having a high melting point / glass transition point, is preferable from the viewpoint of heat resistance. Aromatic polyesters suitable for use include polyethylene terephthalate, polyethylene-2,6-naphthalate, polytrimethylene terephthalate, polybutylene terephthalate and copolymers thereof.

  The release film of the present invention has no organosilicon compound attached on both sides. If there is adhesion of an organosilicon compound, even if it is on the back side, it is preferable to transfer to the surface that becomes the cast surface when rolled up, which may cause contamination of the cast product. Absent. In order to eliminate the adhesion of organosilicon compounds, not only the materials that do not contain organosilicon compounds are used, but also the processing environment, for example, the release material is laminated by coating for the release surface treatment. In some cases, it is necessary not to use a compound containing silicone in the series or in the vicinity.

  The release film of the present invention is one in which at least one surface is mainly composed of polyolefin. As the polyolefin, polyethylene, polypropylene, polybutene, polyhexene, or the like, or a copolymer of these can be used. From the viewpoint of heat resistance, the use of high melting point polyolefin seems to be suitable at first glance, but at the same time, because of its rigidity, peeling becomes heavy, so the polyolefin used here is a copolymer of some other components rather than a homopolymer. Are preferred. However, as the crystallinity is reduced, it is inferior in heat resistance as it is, so even if it is exposed to a high temperature above the melting point by treatment such as forming a crosslinked structure within the range that does not impair the releasability, it does not easily cause a melt flow It is necessary to do so. As a method for forming a crosslinked structure of polyolefin, for example, as described in JP-A No. 2004-82728, there is a method in which a part of polyolefin is made into a reactive polyolefin and this is crosslinked with a polyfunctional compound. .

  The heat peeling force of the surface mainly composed of polyolefin is 80 mN / cm or less, preferably 70 mN / cm or less, more preferably 60 mN / cm or less. When the heat peeling force exceeds 80 mN / cm, it is not preferable because, when the cast molded sheet is peeled off on the surface, there is a possibility that the cast molded article may be stretched. There is no particular lower limit to the preferred range of the heat peel force, but the heat peel force is usually not affected by treatments such as controlling the crystallinity of the polyolefin to make it as soft as possible, or making the polyolefin surface layer as thin as possible. It does not fall below 30 mN / cm.

  The release film of the present invention preferably has a haze of 20% or less after oven heat treatment at 160 ° C for 5 minutes. If the haze exceeds 20%, an error may occur in the step of optically detecting a foreign matter or a defect after cast molding is performed using the haze. Since the polyolefin release layer is roughened by heat treatment when the film thickness increases, a thin film formed on the base polyester by a method such as coating in order to suppress haze change due to oven heat treatment at 160 ° C. for 5 minutes. It is desirable that A criterion for a sufficient thin film is that the absolute reflectance of the release surface does not take a maximum in the wavelength range of 350 to 800 nm.

In the release film of the present invention, it is desirable that the number of foreign matters having a size of 0.2 mm or more is less than 1 per 100 m ² . If the presence probability of the foreign matter exceeds this, it is not preferable because various properties of the molded product may be impaired during cast molding.

  In the formation of the electrolyte membrane, the pressure sensitive adhesive sheet, and the like, when the anti-cast surface side of the cast molded article has adhesiveness or tackiness, it is necessary to attach a release film to the back side after the cast molding. The release film of the present invention is also suitable for protecting the anti-cast surface side.

  Alternatively, instead of using two release films, both surfaces of the release film used as the cast substrate may be release surfaces that satisfy the requirements of the present invention. In the case of a double-sided release film, it is required to control which release surface is used when the product wound up in a roll is unwound. Therefore, it is desirable that the heat release force of the release surface used for the cast surface is surely greater than the normal release force of the release surface on the back side. The polyolefin release layer of the present invention is preferably used even when the release layers on both sides have the same configuration because the heat release force is nearly twice as heavy as the normal release force.

  The release film of the present invention is particularly suitable as a base material for casting such as an electrolyte membrane, and its industrial value is very high.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to a following example. In the examples and comparative examples, “parts” means “parts by weight” as a solid content. The evaluation method used in the present invention is as follows.

(1) 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 points, 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 ratio of silicon-derived silicon atoms to carbon atoms was calculated assuming that the atomic sensitivity coefficients were C (1S) = 1.0 and Si (2S) = 0.86.

(2) Measurement of peeling force Acrylic adhesive tape “No. 31B” (manufactured by Nitto Denko Corporation) is attached to the surface of the release layer, and heat treatment is performed in a hot air oven at 100 ° C. for 1 hour. After the heat treatment, it was allowed to cool at room temperature for 1 hour, and then peeled by 180 ° at a tensile speed of 300 mm / min with a tensile tester, and the value obtained by dividing the average peel load in the stable peel area by the width of the adhesive tape did. No. After 31B is pasted, oven heat treatment is not performed. After leaving at 23 ° C. for 1 hour, 180 ° peeling is performed at a tensile speed of 300 mm / min with a tensile tester, and the average peeling load in the area where peeling is stable is divided by the width of the adhesive tape. The value obtained was defined as the normal peel force.

(3) Measurement of haze The haze of the release film was measured in accordance with JIS K 7136.

(4) Confirmation of reflectance maximum A black vinyl tape (No. 21; manufactured by Nitto Denko) is bonded to the back of the measurement surface, and 350 to 800 nm using a spectrophotometer (UV-3100PC; manufactured by Shimadzu Corporation). The 5 ° absolute reflectance of the measurement surface in the wavelength region of was measured to confirm whether the reflectance was a maximum. When there was a maximum, the wavelength at which the maximum was reached was quantified as λ _max .

(5) Evaluation of foreign matter Visual inspection of 300 m ² was performed, and foreign matters having a size of 0.2 mm or more were counted, divided by 3, and the number of foreign matters per 100 m ² was measured.

(Comparative Example 1)
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 A. Using a Class 100 clean coater, apply the coating solution on both sides using a Mayer bar # 6 on a polyester film (Diafoil T100-50; manufactured by Mitsubishi Chemical Polyester Film) and heat-treat at 130 ° C. for 1 minute. A release film was obtained. In addition, the surface coated first was made into A surface, and the surface coated next was made into B surface.

  A release film was obtained in the same manner as in Comparative Example 1 except that Mayer Bar # 3 was used.

(Comparative Example 2)
Metallocene polyethylene (kernel KS340T; manufactured by Nippon Polyethylene), ethylene / propylene rubber (EP02P; manufactured by JSR) and toluene (Wako Pure Chemical) were mixed at a weight ratio of 800: 800: 98400 to prepare coating solution B. . A release film was obtained in the same manner as in Example 1 except that the coating liquid B was used in place of the coating liquid A.

A release film was obtained in the same manner as in Example 1 except that it was carried out with a class 100,000 coater.
The obtained results are summarized in Table 1 below.

  The film of the present invention can be suitably used as a release film used for production of an electrolyte membrane used for, for example, a fuel cell.

Claims (1)

A film having a polyester film as a main structure, wherein a peak derived from an organosilicon compound is not detected in any surface by X-ray photoelectron spectroscopy measurement, and at least one surface is mainly composed of polyolefin, and the surface A release film having a heat peeling force of 80 mN / cm or less.