JPS645537B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester film that has good mold releasability and slipperiness obtained by coating the surface, and also has excellent antistatic properties. The present invention maintains excellent mold releasability over a long period of time for thermosetting molding resins, catalytic reaction molding resins, ceramics before firing, etc. that are cast or cast under various conditions.・It provides a releasable sheet made of polyester film that can be developed. Polyesters synthesized from aromatic dibasic acids or their ester-forming derivatives and diols or their ester-forming derivatives (e.g., polyethylene terephthalate, its copolymer polyalkylene naphthalate, or blends thereof with small proportions of other resins) The film, which is produced by extruding and biaxially stretching the body), has excellent physical properties, heat resistance, gas barrier properties, electrical properties, and chemical resistance, so it is used in magnetic tapes, X-ray photography, foil-wrapped metallized capacitors, and chemicals. It is used in a wide variety of applications such as pine, diazo film, OHP, FDC, packaging materials, and agricultural materials. One of the fields in which it is used is as a partition wall base material, ie, a mold release sheet, in reactive molding resin molding. This is because the polyester film is biaxially stretched and has high surface cohesion due to crystal orientation, so it generally has poor receptivity to paints, adhesives, and inks, and this inert surface condition can be effectively removed. It can be said that this is a field of application where it is used for many purposes. When used as a mold release material during molding of polyester film and FRP, it can be said that the mold release properties at the interface between the FRP resin and the mold release material are generally good.
However, depending on the FRP curing conditions, the mold release effect may be poor in some areas and the resin and mold release material may adhere to each other, or if the sheet molding resin is heated, Adhesion may occur between the release material film and the resin, which is not always satisfactory. When a release film with such problems is mechanically wound, depending on the thickness of the film, it may break or break.
This may cause delamination or significantly damage the surface of the molded product, reducing the product value. The above problem is caused by repeating the same sheet material 2~
This problem is particularly likely to occur when the resin is used three times, and the problem is also likely to occur when the molding temperature of the resin is raised to accelerate curing. This tendency is influenced by the molecular weight of the polyester constituting the film, the presence or absence of a copolymer, and the type and amount of filler added. Furthermore, local variations in the stretching ratio, crystallization temperature, etc., which are the conditions under which the film was manufactured, have a subtle effect on the film surface. Although good peeling occurs under certain working conditions, partial release defects may be observed under other conditions. On the other hand, the peelability of these sheets differs depending on the FRP molding material, so
It can be said that it is extremely difficult to provide a polyester film with mold releasability that can be used in all cases just by considering the film forming conditions. Despite the industry's desire for a film with good mold releasability that can be used repeatedly under various thermosetting resin molding conditions, for the reasons mentioned above, A film with perfect releasability has not yet been obtained. Examples of sheet materials with mold release performance that can replace polyester film include silicone release paper and polytetrafluoroethylene resin sheets. However, the former is not suitable because it has problems in terms of heat resistance, and the inherent characteristics of paper include a large decrease in strength in a wet state and weakness against flexible tearing. Although the mold releasability of tetrafluoroethylene resin sheet material is good,
As a film, it is opaque, so the internal properties cannot be observed, and it is expensive, so it cannot be called a general-purpose material. Further, although the copolymer has excellent transparency and heat resistance, it has the disadvantage of large thermal deformation, so it cannot be said to be a suitable mold release material. Therefore, attempts have been made to utilize the properties of polyester film to impart mold releasability to its surface. For example, a thin layer of silicone resin is applied to the surface. However, in this coated film, the release agent does not spread uniformly over the surface of the film during manufacture, and tends to become speckled. If the coating film is formed unevenly, the release agent may be transferred to the processed product, which is one of the drawbacks of this coated film. Furthermore, another drawback is that it does not prevent static electricity damage (dust entrainment, etc.) when peeling off the release sheet, and when the peeling operation is stopped, the release sheet may return due to static electricity. There are also operational obstacles. The present invention was developed as a result of extensive research into a sheet (film) that has both release performance and antistatic properties. The present invention provides (a) on one or both sides of a polyester film before stretching orientation is completed, a polyester film that has been stretched and oriented but has not undergone heat treatment crystallization, or a polyester film that has undergone oriented crystallization. A colloidal solution obtained by mixing silicon tetrachloride and a monovalent aliphatic alcohol in a lower alkyl ester solvent and (b) methylhydrogen polysiloxane, dimethylpolysiloxane, methylphenylpolysiloxane, chlorinated phenylpolysiloxane A composition (paint) mixed with a solution containing at least one polysiloxane selected from the group of
A releasable polyester film coated with The present invention will be explained. A partial hydrolyzate solution of silicon tetrachloride, which is an important component of the present invention, is usually prepared by mixing a monohydric alcohol with a lower alkyl ester, and gradually adding silicon tetrachloride to the lower alkyl ester. It is obtained by reacting with water. In order to form a good coating film, it is preferable to use a colloidal solution in which the colloidal particles in the system are in the range of 40 to 80 Å when measured by small-angle X-ray scattering. If the colloid particles are outside the above range, the stability of the liquid may be lowered, the formed film may become cloudy, or craze may occur, which is undesirable. In addition, if it is less than 40 Å, it has the negative effect of delaying the development of antistatic effect or suppressing the exudation of polysiloxane as a composition, so it is extremely important that the size of the colloid particles is within the above range. be. The polysiloxane that is compatible with the partial hydrolyzate solution of silicon tetrachloride is a silicone oil with a viscosity of about 1 to 10,000 cp (centipoise), and includes methyl hydrogen polysiloxane, dimethyl polysiloxane, and methyl phenyl polysiloxane. , chlorinated phenylpolysiloxane, dimethylpolysiloxane and polyoxyalkylene copolymers, and copolymers of polysiloxane and various organic compounds. Since all of these have the effect of imparting mold release properties to the surface, they are included in the composition. The specific gravity is 0.60, which is well compatible with the partial hydrolyzate of silicon tetrachloride, and gradually bleeds in a very small amount onto the surface of the glass-like silica film formed there, so that the mold release effect is maintained. Particularly preferred are dimethylpolysiloxanes having a viscosity of 2 to 50 CP (25°C). When the solvent is removed from a partial hydrolyzate solution of silicon tetrachloride and a glass-like inorganic hard film is formed, this dimethylpolysiloxane is coated continuously in a very small amount necessary to exhibit mold release properties. This is based on the fact that it is particularly superior to other polysiloxanes in that it leaches onto the membrane surface and does not impair the antistatic effect. Furthermore, when this dimethylpolysiloxane is added to a partial hydrolyzate solution of silicon tetrachloride, it is well compatible with the solution, and the addition of this dimethylpolysiloxane may delay the formation of a coating film, cause repellency, or cause a coating film to form. It does not bind and has high affinity and compatibility. A substance that essentially has mold release properties is interposed in melted polyethylene terephthalate to form a film, and this is allowed to ooze out to the surface layer to provide a mold release effect on the surface, and the above mold release properties are added to the paint binder. Although it is possible to bring about a release effect by mixing a static substance and coating it on a polyester film, it has not been possible to simultaneously develop antistatic properties. For example, even if a substance with mold releasability is mixed into an organic paint binder and coated on a polyester film to exhibit mold releasability, this cannot be used as a barrier wall material for a thermosetting molding resin. In some cases, the mold release effect is lost after one or two uses. As described above, even if an organic film is a thermosetting type, there are limits to its heat resistance and solvent resistance, so when it is used repeatedly, the mold releasability deteriorates with each use. In contrast, the mold release layer of the present invention is a glassy inorganic film that has excellent heat resistance and solvent resistance, so it can maintain mold release properties for a long time unless the film is physically damaged. It is. However, if a combination of an inorganic material that forms a hard film and dimethylpolysilexane is used, it is not always possible to obtain at least the same effect, and the adhesion of the paint film may be inhibited or the film may separate. Typeability may be insufficient. In this way, a coating film with reluctance occurs, and it is extremely difficult to maintain a sufficient balance of properties as a release film. This is achieved by combining the aforementioned polysiloxane with a solution in which silicon tetrachloride is partially hydrolyzed in a monohydric aliphatic alcohol and a lower alkyl ester. When applying the composition specified in the present invention to a polyester film, it may be applied to a biaxially stretched film that has undergone crystal orientation, or to an unstretched (non-crystalline) film obtained immediately after casting. Of course, it may also be a film that has been subjected to uniaxial stretching and has not yet been subjected to second axial stretching. Formation of a film with this composition is carried out by completely evaporating the solvent from the solution, but unlike in the case of film formation with an organic binder, phenomena such as foaming do not occur, so that the base material can be spread over a large area. Relatively rapid drying is possible as long as there is no shrinkage. This makes the application process much easier. When applying the composition onto a polyester film, there is no need to use any special method, and any known coating method may be used. That is, reverse coating, kiss coating, air knife coating, spray coating, brush coating, gravure coating, etc. can be applied. Regarding this composition, it is particularly prohibited to use additives such as colorants, fillers, catalyst stabilizers, etc., as long as they do not interfere with the effect of simultaneously imparting antistatic properties and mold release properties, which are the most important features of the present invention. No problem. In addition, the polyester film must be previously subjected to activation treatment such as corona treatment or plasma treatment, matte processing, embossing processing, sandblasting processing, etc. in order to obtain a higher degree of adhesion with the composition of the present invention. Of course, there is nothing wrong with that. The coating thickness of the composition used in the present invention may be the minimum thickness that exhibits its efficacy, and there is no need to make it extremely thick. The preferred thickness is in the range of about 0.1μ to 2μ. The amount of dimethylpolysiloxane contained in the coating composition applied to the present invention is preferably in the range of about 0.5% to 20% based on the total solid content contained in the solution. In order to exhibit particularly good performance, the amount of dimethylsiloxane is preferably in the range of about 5% to 13%. The present invention will be further explained by giving Examples. In addition,
The scope of the present invention is not limited to the examples. The surface properties of the release polyester film obtained by applying the coating composition of the present invention were evaluated by the following method. (Surface Evaluation Method) A. Film Appearance The transparency and presence or absence of coating unevenness were examined with the naked eye, and those with good transparency and no coating unevenness were marked (〇); those with poor appearance were marked (x). B. Antistatic property Surface resistance after being left at 20℃ and 60%RH for 24 hours is 10 ¹² Ω or less (○); 10 ¹² - 10 ¹⁵ Ω is (△); 10 ¹⁵ or more is (x) . C. Peelability Measure the adhesive strength with Scotch adhesive tape #54 using the T-peel method, and if the width is 50 g/cm or less (〇); 50
~150 g/cm width was defined as (△); 150 g/cm width or more was defined as (×). E FRP surface appearance Place a 150 x 200 mm glass fiber woven cloth on the release-treated surface. On top of this, 0.8 parts by weight of methyl ethyl-ketone peroxide was added as a catalyst to 100 parts by weight of an ordinary unsaturated polyester resin (Rigorak 2064) used for FRP corrugated sheets.
Furthermore, the resin is impregnated with 0.5 parts by weight of cobalt naphthenate as an accelerator, taking care not to introduce air bubbles. The film was cured by heating at 110° C. for 10 minutes, and the film was peeled off after being left to cool at room temperature. The resin surface from which the film was peeled off was observed with the naked eye and evaluated for surface irregularities, cloudiness, etc. Good results were marked (○); poor results were marked (x). E. Number of uses The FRP surface appearance evaluation operation was repeated on the same film surface, and the number of times the film was used until it could no longer be used as a release film due to resin adhesion, delamination, etc. was indicated. Example 1 (Preparation of silicon tetrachloride colloidal solution)...Process A 45.9 parts by weight of ethyl acetate and 50.4 parts by weight of ethyl alcohol
Add parts by weight. While stirring this, add silicon tetrachloride.
Add 3.7 parts by weight and leave for 72 hours after addition.
The solution became completely transparent in appearance, and the particle size of the colloidal particles determined by light scattering was about 62 Å. (Preparation of composition paint)...B Add 8 parts by weight of n-butyl alcohol to 32 parts by weight of isopropyl alcohol, and add specific gravity to this mixed solvent.
Add 0.3 parts by weight of dimethylpolysiloxane with a viscosity of 0.61 and a viscosity of 17 CP (25°C) and stir to dissolve. This solubility was added to 60 parts by weight of the colloidal solution of silicon tetrachloride prepared using Process A and thoroughly stirred. (Coating) The coating composition prepared in Process B was coated on a 36 μm biaxially stretched polyester film at a solid content of 0.2 g/m ² using a Meyer bar coater, and heated at 80°C.
Dry for 60 seconds in a hot air dryer. This coated film was subjected to the above evaluation and the results are shown in Table 1. Example 2 Dimethylpolysiloxane (specific gravity = 0.65, viscosity =
A solution obtained by dissolving 0.06 parts by weight of 16.5CP) in a mixed solvent with a ratio of isopropyl alcohol to n-butyl alcohol of 8 to 2 was added to 73.5 parts by weight of the colloidal solution prepared in Process A of Example 1 with stirring. A coating composition was prepared. This paint was applied at a solid content of 0.3 g/m ² using a Mayer bar coater, and dried for 20 seconds in a hot air dryer at 80°C. The coated film was subjected to the above evaluation and the results shown in Table 1 were obtained. Comparative Example 1 A biaxially stretched polyester film was used in its original form without coating, and evaluated as a release barrier material. The results are shown in Table 1. Comparative Example 2 In the formulation shown in Process B of Example 1, the experiment was carried out under exactly the same conditions as in Example 1, except that the amount of dimethylpolysiloxane added was 0.56 parts by weight. The results are shown in Table 1. Comparative Example 3 In the formulation shown in Process A of Example 1, the stirring conditions were changed to reduce the colloidal particle diameter to approximately 200 Å after the formulation.
And so. Other conditions were exactly the same as in Example 1. The results are shown in Table 1. Comparative Example 4 Acrylic resin (Hytaloid 2405
) and 1 part by weight of Melan 20 were added and dissolved. Furthermore, 0.6 part by weight of the dimethylpolysiloxane used in Example 1 was added and thoroughly stirred and dissolved to prepare a composition paint. This paint was applied using a Mayer bar coater at a solid content of 0.5 g/m ² and heated in a hot air dryer at 100° C. for 3 minutes to cure. After cooling to room temperature, the above evaluation was performed and the results shown in Table 1 were obtained.

【table】

[Table] Example 3 The release paint prepared by Process A and Process B of Example 1 was applied to a longitudinally stretched polyethylene terephthalate film (thickness 126μ) at a solid content of 0.7 g/m ² and dried at 80°C for 60 seconds. Next, a biaxially stretched polyethylene terephthalate film having a coating layer was obtained by stretching 3.5 times in the transverse direction in a heated atmosphere at 110°C. When this coated film was evaluated, the results shown in Table 1 were obtained. It is clear that according to the present invention, a polyester film having excellent antistatic effect and mold releasability can be obtained.

Claims (1)

[Claims] 1. A composition obtained by mixing a polysiloxane solution with a colloidal solution obtained by mixing silicon tetrachloride and a monovalent aliphatic alcohol in a lower alkyl ester solvent is coated on the surface of a polyester film. A releasable polyester film. 2. The polysiloxane solution according to claim 1, wherein the polysiloxane solution contains any one of methylhydrogen polysiloxane, dimethylpolyxane, methylphenylpolysiloxane, and chlorinated phenylpolysiloxane. Releaseable polyester film. 3. The releasable polyester according to claim 1 or 2, wherein the main component of the solution is dimethylpolysiloxane having a viscosity of 2 to 50 centipoise at 25°C and a specific gravity of 0.60 to 0.97 at 25°C. film. 4. A polyester film that has not yet been completely stretched and oriented, or a polyester film that has been stretched and oriented but has not undergone heat treatment and crystallization, and is coated with a composition on at least one side of the polyester film and subjected to stretching heat treatment. A releasable polyester film according to scope 1.