JP5155544B2 - Polyester film for manufacturing silicone rubber sheets - Google Patents

Description

  The present invention relates to a polyester film that can be suitably used for producing a matt and rough silicone rubber sheet.

  Polyester films typified by polyethylene terephthalate are excellent in mechanical strength, dimensional stability, heat resistance, chemical resistance, cost performance, etc., and are therefore used as process films and surface protective films in various applications. As an example of the application, there is a process film or a protective cover film used for manufacturing a silicone rubber sheet used for a membrane switch sheet, a buffer material sheet, or the like of various electronic devices.

  Silicone rubber sheets are usually soft, so that they are very slippery when used and are also easily soiled. Therefore, the surface is processed into a matte shape according to the application, and the handling is improved or the protective film is attached and sold, and the protective film is peeled off when used by the customer or when the device is installed. Often taken.

  The most efficient way to obtain a matte silicone rubber sheet is to use a roughened polyester film as the process film, and then cast or apply uncrosslinked silicone rubber on it, or apply it to the surface of the uncrosslinked silicone rubber sheet. A method of laminating and laminating a roughened polyester film and curing and crosslinking in a subsequent process as it is and transferring and forming the rough surface shape on the surface of the silicone rubber sheet can be mentioned. The polyester film can be used as it is as a protective cover film if the laminated film is left after the post-curing / crosslinking treatment.

  In addition to the polyester film substrate, use of a polypropylene film, a fluororesin film, an acrylic film, or the like has been proposed as the process film, but the use of a polyester film is desirable in terms of strength, heat resistance, and cost.

  As a means for producing a roughened polyester film, a method of forming a film using a polyester resin raw material to which several percent of inorganic or organic particles are added (kneading mat), a paint having particles added to the surface of the polyester film Applying and drying to form a roughened surface (coating mat), spraying fine inorganic sand on the surface to roughen the surface (sand mat), or chemically eroding the polyester film surface with chemicals There are methods.

  By such means, a roughened polyester film can be obtained. When this roughened polyester film is used as a process film, the roughened polyester film is removed from the surface of the cured and crosslinked silicone rubber sheet. When peeling, the peelability is not sufficient, and when the silicone rubber sheet is thin, various troubles of peeling work are likely to occur. Therefore, a roughened polyester film having appropriate peelability is desired for use in silicone rubber sheets.

JP 10-53659 A JP 2001-71407 A JP 2004-122621 A

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the polyester film for silicone rubber sheet manufacture which can give moderate surface roughness and peelability at low cost. is there.

  As a result of repeated studies in view of the above circumstances, the present inventor has found that the above problem can be easily solved by a polyester film having a specific configuration, and has completed the present invention.

That is, the gist of the present invention is that, on the surface of a polyester film having an arithmetic average surface roughness (Ra) of one surface of 0.3 to 1.5 μm, a C ₉ F ₁₇ O-group is attached to a terminal or a side chain. Or a polyester for producing a silicone rubber sheet, having a coating layer having a thickness of 0.05 to 0.5 μm, which contains a compound having a C ₆ F ₁₁ O— group and a melting point of 30 ° C. or more as a main component. Be on film.

Hereinafter, the present invention will be described in more detail.
For silicone rubber, silicone rubber compounds (cured / crosslinked by adding vulcanizing agent and heated), two-part liquid silicone rubber (addition polymerization and cured / crosslinked by heating together with curing catalyst component) from each manufacturer , Two-component RTV rubber (condensation or addition polymerization by curing catalyst components, curing / crosslinking), one-component RTV rubber (dehydration, deoxime, alcohol removal or acetone-curing / crosslinking by moisture or heating), etc. Depending on the type of processing equipment for silicone molding, it is made into a molded product / sheet by extrusion, injection molding, or coating. Silicone rubber has molding and fluidity in an uncrosslinked state, but becomes a rubber body having shape retention after crosslinking. It is possible to modify the properties and characteristics according to the use by adding inorganic additives, blending, etc., but all have basic characteristics as silicone rubber. Further, in recent years, as a means for efficiently crosslinking an uncrosslinked silicone rubber in a short time, especially for a sheet-like material, crosslinking by electron beam irradiation / radiation irradiation is also common.

  The polyester used in the present invention is obtained, for example, by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. 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 polyesters include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). The polyester may be a homopolyester or a copolyester. In the case of a copolyester, it is a copolymer containing usually 30 mol% or less of the third component.

  The polyester used in the present invention may be obtained by a melt polymerization reaction, or may be obtained by solid-phase polymerization of a chip-formed polyester after melt polymerization.

  In the present invention, it may be a single layer structure film or a film having a structure in which different types of polyesters are coextruded and laminated, and any polyester layer is within the range that does not impair the gist of the present invention. If present, an antistatic agent or the like may be blended.

  In order to adjust the roughness of the film surface, inert inorganic or organic fine particles are added to the polyester. The particles to be blended include silicon oxide, alumina, calcium carbonate, calcium phosphate, kaolin, and titanium oxide. , Barium sulfate, lithium fluoride, talc, crosslinked polymer fine powder, and the like. These particles may be used alone or in combination of two or more components.

  As for the particles added here, the average particle size (value measured by centrifugal sedimentation) is usually 0.5 to 15 μm, preferably 1.0 to 10 μm, when roughening is obtained. Is selected.

  For single-layer films (for multi-layer films, in the target surface layer), the content of particles added for roughening is usually in the range of 0.3 to 15% by weight, but effective In order to obtain a good surface roughness, it is preferably in the range of 1 to 10% by weight. When the content of the particles is small, sufficient surface roughness cannot be obtained, and when the content of the particles exceeds 15% by weight, stable production of the roughened polyester film becomes difficult. .

  As for the roughened polyester film, a kneaded matte film in which particles are added to the polyester film layer as described above is desirable in terms of cost or quality, but a sand obtained by sandblasting the surface of the polyester film. It may be a matte film or a coated matte film obtained by applying a resin paint to which particles are added to a polyester film.

  The arithmetic average surface roughness (Ra) of one surface of the polyester film that is the film substrate of the present invention needs to be in the range of 0.3 to 1.5 μm. When Ra is less than 0.3 μm, the intended roughening transfer effect is weak, and the slipperiness and handling properties of the silicone rubber sheet are not sufficiently improved. On the other hand, when the Ra value exceeds 1.5 μm, it becomes difficult to stably obtain a roughened polyester film.

  Next, as examples of the method for producing a polyester film of the present invention, examples of a kneaded mat film and a coating mat film will be shown. Not. Moreover, the addition of particles having an average particle size of 0.5 μm or more for roughening can be carried out at any stage from the polyester polymerization step to the polyester film production step.

  Bis-β-hydroxyethyl terephthalate (BHT) is obtained by esterification from terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol according to a conventional method. Next, this BHT is transferred to a polymerization tank, the pressure is gradually reduced, and the reaction proceeds while the temperature is raised. Finally, the polymerization reaction is carried out at a temperature of 280 ° C. under vacuum to obtain a polyester raw material.

  This polyester raw material is extruded as a molten sheet from a die using an extruder, and cooled and solidified with a cooling roll to obtain an unstretched sheet. The unstretched sheet is stretched in the first stage by a roll or 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. Next, stretching is performed in a direction orthogonal to the first-stage stretching direction. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 115 ° C., and the stretching ratio is usually 3.0 to 6 times, preferably 3.5 to 5 times. Subsequently, heat treatment is performed at a temperature in the range of 130 ° C. to 250 ° C. under a relaxation of 30% or less to obtain a biaxially stretched polyester film.

  Various thicknesses can be selected as the thickness of the polyester film as the substrate of the present invention depending on the use, but in the present invention, the thickness is suitably in the range of 25 to 125 μm.

  In the present invention, in order to impart appropriate peelability to the silicone rubber sheet to the polyester film of the base material, the main component is a compound having a fluorine-containing group at the terminal or side chain and having a melting point of 30 ° C. or higher. It is necessary to have the layer in a thickness range of 0.05 to 0.5 μm. The coating layer can be formed by an in-line coating method or an offline coating method.

  The in-line coating is a method of applying a paint in the film forming process, and the off-line coating is a method of applying and drying the paint by applying the polyester film obtained in the film formation to a coater.

  Examples of paint application methods include roll coating, gravure coating, micro gravure coating, reverse coating, reverse gravure coating, bar coating, roll brushing, air knife coating, curtain coating, and die coating. Any coating method may be applied singly or in combination as appropriate.

  As a compound having a fluorine-containing group at the terminal or side chain and having a melting point of 30 ° C. or higher after drying, various wax-like or solid fluorine-based compounds, or those containing them as main components in various binders And fluorine-based graftmers having an acrylic skeleton.

  If the thickness of the coating layer is less than 0.05 μm, the effect of imparting peelability is weak when coated on a roughened polyester film, while if it exceeds 0.5 μm, unevenness in surface roughness transfer occurs. Moreover, since a fluorine-type compound is expensive, it will raise a cost.

  In the relationship between the Ra value of the polyester film and the coating thickness, when the coating thickness is larger than the Ra value (μm), surface roughness transfer inhibition may be a problem.

In the present invention, the composition fluorine-based compound having a fluorine-containing group at the terminal or side chain and having a melting point of 30 ° C. or higher after drying can be used particularly effectively as α-perfluorononenyloxy-ω- Perfluorononeryl polyethylene oxide: C ₉ F ₁₇ O (CH ₂ CH ₂ O) _n C ₉ F ₁₇ (n is 45 on average), α-perfluorononenyloxy-ω-methyl polyethylene oxide: C ₉ F ₁₇ O (CH ₂ CH ₂ O) _n CH ₃ (where n is 2 to 20), those having C ₉ F ₁₇ O— groups at both ends, those having C ₆ F ₁₁ O— groups, or these There are things that have at one end, for example, each brand of Footage sold by Neos Co., Ltd., FTX-233F, FTX245F, FTX-220S, FT 230S, FTX-245M, and the like can be used FTX-290M.

  In addition, as a fluorine-based graft polymer having an acrylic skeleton, for example, Aron GF-300 manufactured by Toagosei Co., Ltd. can be used.

  Usually, these coating agents can be used after appropriately diluted with a solvent such as toluene, MEK, or methanol (water in the case of an aqueous type). The effect can be obtained by mixing these with other resin binders or solidifying them integrally.

  Although the transfer of the coating component is suppressed by the surface irregularities of the polyester film, if the melting point after drying is less than 30 ° C., the film becomes sticky due to the transfer of the coating component, which is not preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester film for silicone rubber sheet manufacture which can provide moderate surface roughness and peelability can be provided, and the industrial value of this 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. In addition, the evaluation method of the various characteristics in this invention is as follows.

(1) Arithmetic mean roughness (Ra)
In the case where the surface of the film is provided with a coating layer on the surface, the coating film is peeled off with a cotton containing a solvent (for example, toluene) (for example, manufactured by Asahi Kasei) or an absorbent cotton, and the exposed surface is removed. Using a surface roughness measuring instrument SE3500 manufactured by Kosaka Laboratory Ltd., measurement is performed under the following conditions based on JIS B0601, and calculation is performed.
<Measurement conditions>
Measurement length 2.5mm, feed rate 0.1mm / sec, cut-off value 0.08mm

(2) Silicone rubber sheet peelability Shin-Etsu Chemical Co., Ltd. 2-pack type liquid silicone rubber: KE1990 solution A and solution B were mixed at a weight ratio of 1: 1, and applied to a sample film with a coating thickness of 500 μm. After drying / curing / crosslinking treatment at 150 ° C. for 10 minutes, the laminate is left in a room at 23 ° C. for 1 day, cut to a width of 50 mm, and the polyester film is peeled off from the silicone rubber sheet. The peelability is evaluated according to the following criteria.
◯: The laminate can be easily peeled off (180 degree peeling force measured at a peeling speed of 300 mm / min is less than 300 mN / cm, and the peeled silicone sheet surface becomes a uniform matte surface. Yes)
X: It is heavy to peel off the laminate, leaving traces or fouling (peeling force exceeds 300 mN / cm)

(3) Silicone rubber sheet handling property A silicone rubber sheet having a rough surface formed of roughened polyester is cut into 5 cm squares, placed on a flat glass surface with the roughened surface facing down, and the silicone sheet is pressed with a finger. To determine if the sheet easily slides on the glass surface.
◯: Good sliding, easy handling, no problem in actual use ×: Sheet sticks to the glass surface, poor sliding, and poor handling, causing problems in actual use

Example 1:
Pellets of polyethylene terephthalate (added 3% by weight of silica particles with an average particle size of 3 μm) are crystallized by hot air drying at 180 ° C., then fed to an extruder, and melt extruded from a T die into a sheet at a temperature of 280 to 300 ° C. The film was cast and quenched on a mirror-cooled drum in combination with an electrostatic adhesion method to obtain an unstretched film having a thickness of about 613 μm. Subsequently, this film was stretched 3.5 times in the longitudinal (longitudinal) direction at 85 ° C. to obtain a uniaxially stretched film. Subsequently, the film is stretched 3.5 times in the transverse direction at 110 to 150 ° C. in the transverse stretching zone, and heat treated and fixed at 230 ° C. to obtain a biaxially stretched polyester film (1) having a thickness of 50 μm and Ra of 0.5 μm. It was. The following peelable coating was applied to this film with a coater and passed through a drying furnace at 130 ° C. for a passage time of 20 seconds to obtain a polyester film (1A) having a coating amount of 0.1 g / m ² after drying. Table 1 below shows the results of evaluating the applicability of the polyester film (1A) to the silicone rubber sheet.
[Peelable paint]
C ₉ F ₁₇ O (CH ₂ CH ₂ O) _n C ₉ F ₁₇ (n is an average of 45) (melting point: about 40 ° C.): 1 part by weight MEK / toluene = 1/1 diluent solvent: 50 parts by weight

Example 2:
In Example 1, the following roughening paint was applied to a polyester film (2-1) having a thickness of 50 μm with a reduced amount of silica particles and Ra of 0.03 μm, and the inside of a 160 ° C. drying furnace was applied. A polyester film (2-2) having a coating amount of 3 g / m ² after drying was obtained through a passage time of 30 seconds. The peelable coating material used in Example 1 was applied to the roughened surface of this film so that the coating amount after drying was 0.2 g / m ² to obtain a polyester film (2A) having an Ra of 0.7 μm. It was. Table 1 shows the results of evaluating the applicability of the polyester film (2A) to the silicone rubber sheet.
[Roughening paint]
WASHIN CHEMICAL CO., LTD. Plus coat: SR-4000: 100 parts by weight Curing agent # 30 Dryer: 9 parts by weight Amorphous silica particles having an average particle size of about 3 μm: 10 parts by weight Toluene / MEK / methanol = 3/3 / 1 Diluting solvent: 100 parts by weight

Comparative Example 1:
The polyester film (2-2) obtained in Example 2 was coated with the releasable paint of Example 2 so that the coating amount after drying was 0.03 g / m ² to obtain a polyester film (2B). The applicability to the silicone rubber sheet was evaluated.

Comparative Example 2:
About the polyester film (1) obtained in Example 1, the applicability to a silicone rubber sheet was evaluated.

Comparative Example 3:
About the polyester film (2-1) which does not apply | coat the roughening coating material in Example 2, the applicability to a silicone rubber sheet was evaluated.

Comparative Example 4:

  About the polyester film (2-2) obtained in Example 2, the applicability to a silicone rubber sheet was evaluated.

  The evaluation results of the obtained polyester film are as shown in Table 1, and satisfactory results were obtained for the roughened polyester films of Examples 1 and 2. On the other hand, in Comparative Examples 1 to 4, satisfactory results were not obtained. In this example, the effect on the silicone rubber sheet was confirmed using a sheet made from a liquid silicone rubber, but it was applied to another heat vulcanized silicone rubber sheet or a silicone rubber sheet cross-linked by electron beam irradiation. The same effect can be obtained for this.

  The film of the present invention can be suitably used, for example, for producing a silicone rubber sheet.

Claims (1)

On the surface of the polyester film having an arithmetic average surface roughness (Ra) of 0.3 to 1.5 μm on one surface, a C ₉ F ₁₇ O-group or a C ₆ F ₁₁ O-group is attached to the terminal or side chain. A polyester film for producing a silicone rubber sheet, comprising a coating layer having a thickness of 0.05 to 0.5 μm and containing a compound having a melting point of 30 ° C. or more as a main component.