JP3164470B2 - Method for producing crosslinked silicone film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining a cross-linked film of a polyorganosiloxane (hereinafter sometimes abbreviated as silicone) or a laminated film containing the cross-linked film. The present invention relates to a method for obtaining a cross-linked film by irradiating γ-rays after forming a three-layer film by forming the film into a state sandwiched between two other films.

[0002]

2. Description of the Related Art Hitherto, polyorganosiloxanes have been known under the names of silicone, silicone oil and the like, and have been used in various applications by making use of their performances such as non-toxicity, release property and heat resistance. Among polyorganosiloxanes, those called silicone rubber have a molecular weight of about 400,000-
700,000 viscous polymers, the only material capable of continuous plastic molding. Crosslinked after plastic molding and used as electric wires, hoses, packings, etc. in the electric, automotive and medical fields.

[0003]

However, polyorganosiloxane has a property inherent in its material that has a low material strength in an uncrosslinked state at the time of molding and is limited in plastic molding. Further, in an uncrosslinked state until a crosslinking treatment is performed using heat or radiation in order to impart practical strength, there is a limitation in maintaining a shape after molding. This is particularly noticeable in the case of a thin, low-strength film.

In order to obtain a long film-shaped product, when a cross-linking treatment is performed by irradiation of radiation, a space is required to irradiate a traveling film with an electron beam or γ-ray.
Various auxiliary devices such as a support for the running film, a tension adjusting mechanism, and an environmental purification device for preventing pollution are required. In particular, in the case of γ-rays, when the atmosphere is air (air), oxygen reacts with silicone to inhibit the crosslinking reaction, and the atmosphere is adjusted to an inert gas such as nitrogen to suppress it. It is uneconomical because it takes time and effort.

[0005]

SUMMARY OF THE INVENTION The present invention has solved the above-mentioned problems and has succeeded in cross-linking a silicone film with good productivity and without requiring a large-scale apparatus.
The gist is that the uncrosslinked polyorganosiloxane is molded into a film in a state sandwiched between two other films, and the resulting three-layer laminated film is rolled into a roll to form a gamma ray. A method for producing a crosslinked silicone film, comprising irradiating 1 to 20 Mrad to crosslink a polyorganosiloxane.

According to this method, a film in which a crosslinked silicone film and another film are laminated in a releasable state, or a film in which both are firmly adhered, can be freely obtained. The film can be peeled off or used as it is.

[0007] The silicone (polyorganosiloxane) in the present invention comprises a siloxane unit, Wherein R ₁ and R ₂ are all methyl groups, including polydimethylsiloxane, and a part of methyl groups is substituted with one or more of vinyl group, phenyl group, fluoroalkyl group and the like. It is composed mainly of polyorganosiloxane, and can be a crosslinked silicone film by crosslinking by a known method.

The molecular weight of silicone is 10,000.
７００700,000 can be used, and according to the classification, a low molecular weight oil called silicone oil can be used. Further, as a component other than the above polyorganosiloxane, various compounds necessary for crosslinking can be added. If necessary, reinforcing silica filler such as silica hydrogel and silica aerogel; clay, calcium carbonate, diatomaceous earth , A filler such as titanium dioxide; a conductive agent such as conductive carbon, Ni powder and Ag powder; a thermal conductivity improver such as boron nitride, aluminum nitride, alumina and zinc oxide;
A heat-resistance improver such as iron oxide, cerium oxide and iron octylate; a dispersant such as a low-molecular-weight organosilane compound; and a platinum compound that imparts flame retardancy may be added and mixed.

Desirably, a system containing a vinyl group-containing silicone having a high crosslinking reaction efficiency in consideration of the subsequent crosslinking step (γ-ray irradiation) is preferable, and divinylbenzene, styrene, vinyltoluene, diallyl is used as a crosslinking agent. It is also possible to mix vinyl and allyl compounds such as phthalate, triallyl cyanurate and triallyl isocyanurate.

This polyorganosiloxane is added from both sides to 2
It is shaped into a film sandwiched between other films. Extrusion, calendering, pressing, solution coating and the like can be applied for molding. In the case of the extrusion method, the film on both sides or one side is extruded at the same time, or the film is prepared in advance, and the silicone is extruded from the die as a film by extrusion and discharged, and the film is laminated at the same time. Various methods can be adopted. In the case of the calendering method, two other films are passed through two calender rolls, and silicone is supplied between them.
A method of forming a bank on a calender roll and simultaneously laminating silicone between other films can be employed.

In the case of the press method, silicone is supplied between two other films and pressurized by a press plate, or is continuously pressed between two endless belts. In the case of the solution coating method, a silicone solution is coated on another film and dried, and then another film is laminated from the silicone side. The coating method is not particularly limited as long as it can be coated on one side of the film, such as a doctor coat, an air knife coat, a reverse roll coat, and a gravure roll coat.

[0012] Two other films on both sides, which fix the shape of the uncrosslinked silicone film,
The silicone film is cross-linked as it is, protecting the cross-linked silicone film from external force and contamination, and improving transport, winding, storage, and handling when using the film. A material having high adhesiveness (that is, the films do not adhere to each other when wound into a roll as described below), high strength, and properties that do not impair physical properties necessary for practical use under crosslinking conditions are used.

It is necessary that this film does not absorb γ-rays used for crosslinking in the present invention. However, since γ-rays have almost no absorption loss such as electron beams and X-rays and have high transparency, However, this point is not a problem in practical use.

The other surface characteristics of the film, particularly the characteristics of the surface in contact with the polyorganosiloxane, can be set according to the purpose. For example, when the crosslinked silicone film is finally peeled and used, a material which is non-adhesive to the crosslinked silicone film and is easily peeled is selected.
Specifically, a plastic film sheet such as polyethylene terephthalate or a metal foil such as an aluminum foil, an electrolytic copper foil, or a rolled copper foil is suitable, and generally, a material having a smooth surface is used. For the purpose of improving the releasability from the crosslinked silicone film, a release layer for the crosslinked silicone can be provided on the surface of the hard plastic film sheet or metal foil.

On the other hand, when used in a laminated state, a primer treatment is applied to the cross-linked silicone film so as to be adhesive. As for the method, the film itself may be composed of a material having an adhesive property to the crosslinked silicone, or an ordinary film may be laminated and coated with a material having an adhesive property to the crosslinked silicone.

Examples of such a material include those obtained by grafting or block copolymerizing silicone, those containing a silane coupling agent, and those having a radiation-polymerizable functional group (eg, vinyl group, acryloyl group, etc.). is there. The adhesion between the treated film and the silicone film at the interface between the treated film and the silicone film is improved by the dispersing effect and the chemical bond generated by the subsequent γ-ray irradiation.

The silicone laminated film thus obtained is not cross-linked and has fluidity and tackiness, but is supported by the films on both sides. Relatively good in handling. Since the films on both sides are non-adhesive, it is important that the film can be wound into a roll under tension.

As described above, the polyorganosiloxane having a molecular weight of about 10,000 to 700,000 is preferable from the viewpoint of its flow characteristics.
By adjusting the processing temperature, etc., the film has a viscosity suitable for processing, that is, a film with a uniform thickness when sandwiched between two films, and a fluidity that does not flow out between the two films. Can be set. Furthermore, in the present invention, since the polyorganosiloxane has adhesiveness to the films on both sides when it is not cross-linked, the flow is suppressed to some extent, and even if the laminated film is wound under tension, it will not stain from the side. No good roll is obtained.

This silicone (laminated) film is wound into a roll and then crosslinked by γ-rays. In the case of gamma rays, electron beams that can be industrially used with other radiation,
Although there is not much difference in cross-linking (reaction) properties as compared with the wire, since it is excellent in permeability, a long roll of the laminated film can be cross-linked as it is. Therefore, as compared with irradiating the produced film as it is or while irradiating the wound film while rewinding the film, there is a practically great advantage that the transport device and the like can be simplified and there is no trouble. There is no practical limitation on the size of the roll to be wound, and a final product (wind roll) having various winding lengths can be freely obtained.

Further, by irradiating with γ-rays in a rolled state as in the present invention, the atmosphere does not need to be adjusted to an inert gas (for example, nitrogen or the like), and the atmosphere (air) can be maintained. Can be implemented. In the state where the silicone obtained by general molding (for example, solution coating method, pressing method, etc.) is exposed on the surface instead of the laminated film as in this method, oxygen in the atmosphere inhibits the crosslinking reaction when irradiated under the atmosphere. If the silicone film is too sticky and does not have sufficient strength, or if the silicone film is too stretched, or if you attempt to peel off another film that is laminated for use alone, the peeling is heavy and the silicone film In particular, handling characteristics such as breakage are inferior in handling.

However, when another film is laminated on both sides as in the present method and the silicone is not exposed, the other film is prevented from contacting with excess oxygen which inhibits a crosslinking reaction, so that it is as if the silicone atmosphere is present. Is filled with an inert gas and acts as in an oxygen-free state, so that the crosslinking reaction proceeds sufficiently. In addition, other films on both sides may damage the silicone from outside and prevent contamination,
Silicone undergoes γ-ray sterilization at the same time as γ-ray crosslinking, and also has the effect of acting as a protective film for maintaining the sterilized state.

As other films for irradiating γ-rays in the atmosphere, paper or perforated film through which a large amount of air (oxygen) permeates is not suitable, but ordinary non-porous plastic films can be used without any problem. Can be used. The thickness of this film is 20 to 200 μm in terms of economy and ease of winding.
m is preferable, and if the thickness is in the range, the oxygen permeability coefficient (cc · cm / m ² · sec · cmHg) is 10 ¹²
Films on the order or less are preferred. Specific examples include polyethylene terephthalate, cellophane, polyamide, and polyarylate.

In the present invention, the amount of air (oxygen) dissolved in the material, slightly remaining between the layers, or air entering from the end face of the laminated film is small and does not substantially hinder the crosslinking.

The amount (energy) of gamma ray irradiation is preferably in the range of 1 to 20 Mrad in terms of absorbed dose, and more preferably in the range of 2 to 10 Mrad. If it is smaller than 1 Mrad, the strength is insufficient, and if it is larger than 20 Mrad, there is no change (improvement) in the strength, which is uneconomical. In the present invention, since the γ-rays are irradiated in a state in which the film on both sides is shielded from excess oxygen, the level of the absorbed dose can be generally reduced. This will be described below with reference to examples.

[0025]

【Example】

(Example 1) TSE2571-5U (Toshiba Silicone Co., Ltd., polymethylvinylsiloxane, sticky rubber at room temperature) was supplied along two calenders having a diameter of 100 mm and two two-axles having a thickness of 38 µm. It was put between stretched polyethylene terephthalate films, and a bank was formed on the rolls at a roll temperature of 25 ° C. to form a film having a thickness of 100 μm and laminated simultaneously to form a three-layer laminated film. The laminated film absorbs γ-rays in the atmosphere and the dose is 10 Mra.
Irradiation was performed so as to obtain d, and the silicone film was crosslinked.

The biaxially stretched polyethylene terephthalate film outside the three-layer laminated film thus obtained was peeled off to obtain a single-layer cross-linked silicone film. This film has sufficient strength and has no problem in handling. Was. Tensile test (JIS)
K-6761), and the results are summarized in a table. (Comparative Example 1) After forming a three-layer laminated film in Example,
The biaxially stretched polyethylene terephthalate film on one side was carefully peeled off so that the silicone would not be deformed or destroyed, and the silicone layer was exposed to the outside air, and γ-rays were irradiated under the atmosphere so that the absorbed dose became 10 Mrad to crosslink the silicone film. .

Although the silicone layer of this film is somewhat crosslinked, the silicone surface is more tacky than in the case of the example, and there is a problem in handling properties such as a heavy feel when peeled off into a single layer. Had. The mechanical properties of this silicone single-layer film were inferior to those of the examples.

(Comparative Example 2) After forming a three-layer laminated film in the example, the biaxially stretched polyethylene terephthalate film on one side was carefully peeled off so that the silicone would not be deformed or broken, and the silicone layer was exposed to the outside air, and then exposed to a nitrogen atmosphere. The silicone film was cross-linked by irradiating gamma rays so that the absorbed dose became 10 Mrad.

This silicone single-layer film showed the same mechanical properties as those of the example, but required a nitrogen replacement step.

Comparative Example 3 A three-layer laminated film was formed in the same manner as in the example, and the silicone film was crosslinked by irradiating 0.5 Mrad of γ-ray in the atmosphere. Although the outer film was peeled off to obtain a single-layer crosslinked silicone film, there was a problem in handling properties such as adhesiveness, and the mechanical properties were inferior to those of the examples.

Comparative Example 4 A three-layer laminated film was formed in the same manner as in the example, and the silicone film was cross-linked by irradiating 30 Mrad of γ-ray in the atmosphere. The outer film was peeled off to form a single-layer crosslinked silicone film, but the handling properties and mechanical properties were the same as in the examples. However, γ-ray processing required a great deal of trouble.

[0032]

[Table 1]

[0033]

According to the present invention, the cross-linking is carried out by laminating other films on both sides of an uncross-linked silicone film, winding the film into a roll, and irradiating the film with γ-rays at an appropriate absorbed dose. The handling of the shape retention in the uncrosslinked state until the process is improved, and it is not necessary to adjust to an atmosphere in which crosslinking is easy to proceed, it can be carried out in the atmosphere, and the incidental equipment can be simplified, efficient It becomes possible to provide a crosslinked silicone film or a laminated film thereof.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI // C08L 83:04 (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 3/00-3/28 C08J 7 / 00-7/18 B32B 27/00-27/42

Claims (4)

(57) [Claims] 1. An uncrosslinked polyorganosiloxane is formed into a film in a state of being sandwiched between two other films, and the obtained three-layer laminated film is rolled into a γ form.
A method for producing a crosslinked silicone film, comprising irradiating a line with 1 to 20 Mrad to crosslink the polyorganosiloxane. 2. A non-crosslinked polyorganosiloxane is formed into a film sandwiched between two other films, and a film which is non-adhesive to crosslinked silicone is used as the other two films. The resulting three-layer laminated film was wound into a roll and irradiated with γ-rays from 1 to 20 Mrad to crosslink the polyorganosiloxane, and other films were laminated on both sides of the crosslinked silicone film in a releasable manner. A method for manufacturing a laminated film. 3. An uncrosslinked polyorganosiloxane is formed into a film in a state sandwiched between two other films, wherein at least one inner surface of the other two films is
A crosslinked silicone laminated film, which is subjected to a primer treatment for adhering to a crosslinked silicone, and the polyorganosiloxane is crosslinked by irradiating 1 to 20 Mrad of γ-ray while the obtained three-layer laminated film is wound into a roll. Manufacturing method. 4. The method according to claim 1, wherein the non-breathable film is used as the other two films, and the γ-ray irradiation is performed in the atmosphere.