JPH10175271A - Moldable release sheet and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moldable release sheet which does not shrink or deform during production of a release sheet, is excellent in releasability and moldability, and is useful for packaging materials and the like. SOLUTION: A moldable release sheet in which a layer made of an electron beam-curable silicone compound is provided on at least one surface of a polyester sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moldable release sheet and a method for producing the same, and more particularly to a moldable sheet which is excellent in mold release and moldability and is useful as a packaging material, using a polyester sheet as a base sheet. The present invention relates to a release sheet and a method for manufacturing the same.

[0002]

2. Description of the Related Art A polyester sheet is formed by a thermoforming method such as a vacuum forming method or a pressure forming method, and is used for packaging containers and the like. However, this polyester sheet has a problem that the releasability between the sheets when handling the sheets and the releasability between the containers when the formed containers are stacked are insufficient.

[0003] In order to improve such disadvantages, a method of applying silicone oil as a release agent to the surface of a polyester sheet has been adopted. However, this method has a problem in that the silicone oil is lost from the surface of the polyester sheet during molding or processing, and the releasability is reduced, and the printability of the surface coated with the silicone oil or the surface transferred with the silicone oil is poor. is there.

[0004] In order to improve the above-mentioned problems of the releasability and printability, a method of laminating a thermosetting silicone release layer on a polyester sheet has been considered. It is necessary to heat-treat the mold layer at a temperature of at least 100 ° C. for at least 10 seconds in order to harden the mold layer. For example, in the case of an unstretched polyester sheet, it is deformed by heat shrinkage, crystallization proceeds, and transparency and moldability are increased. Is reduced.

In order to solve these problems, it is effective to form a release layer with an ultraviolet-curable silicone compound. However, in many cases, a reaction initiator or a photosensitizer is required, and foods are required. There is a problem that it is difficult to use the container for a purpose.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide a moldable release sheet having a release layer excellent in mold release properties and durability, and a method for producing the same. Is to do.

[0007]

SUMMARY OF THE INVENTION The present invention has the following configuration to achieve the above object. A. A moldable release sheet in which a layer made of an electron beam-curable silicone compound is provided on at least one side of a polyester sheet. I. A method for producing a moldable release sheet, comprising applying a coating liquid containing an electron beam-curable silicone compound to at least one surface of a polyester sheet and providing a layer formed by irradiating an electron beam. Hereinafter, the present invention will be described in detail.

[Polyester] In the present invention, the polyester constituting the polyester sheet is a linear saturated polyester comprising an aromatic dibasic acid component and a diol component. Examples thereof include polyethylene terephthalate, polytrimethylene terephthalate, and polytetramethylene. Terephthalate, polypentamethylene terephthalate, polyhexamethylene terephthalate, polyethylene-2,6-
Examples thereof include naphthalate, polytetramethylene-2,6-naphthalate, polyhexamethylene-2,6-naphthalate, polytrimethylene-2,6-naphthalate, and polypentamethylene-2,6-naphthalate. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred.

The polyester may be a single polymer or a copolymer obtained by copolymerizing another component as an aromatic dibasic acid component and / or a diol component. Further, a single copolymer or a mixture of two or more copolymers may be used.

[0010] The above-mentioned polyester may be blended with an improving agent such as an antistatic agent or a lubricant. Examples of the antistatic agent include compounds having a sulfonic acid group such as sodium dodecylbenzenesulfonate. The lubricant has an average particle size of 0.01 to
20 μm organic fine particles or inorganic fine particles, for example, 0.00
It can be contained at a ratio of 5 to 20% by weight. Specific examples of such fine particles include inorganic fine particles such as calcium carbonate, kaolin, silicon oxide, and barium sulfate, and organic fine particles such as crosslinked polystyrene resin particles, crosslinked silicone resin particles, and crosslinked acrylic resin particles.

[Polyester Sheet] The polyester sheet in the present invention is preferably a sheet made of a substantially non-oriented and amorphous polyester because the sheet has good moldability. Is more preferable. Further, the thickness of the polyester sheet is preferably from 50 to 500 μm.

[0012] Such a polyester sheet can be produced by a conventionally known method. For example, after drying polyester, it is melted by an extruder, and a die (for example, T
-Die, I-die, etc.) on a cooling body, and quenching to give a substantially amorphous unstretched sheet. As the above-mentioned cooling body, a conventionally used rotary cooling drum is preferable, for example, a cooling drum having metal, plastic, rubber or the like on its surface, and a drum by circulating a liquid or gaseous refrigerant inside the cooling drum. Those having a structure capable of forcibly cooling the surface are particularly preferable.

[Release Layer] In the present invention, a release layer obtained by curing an electron beam-curable silicone compound is provided on at least one surface of the above-mentioned polyester sheet. The release layer preferably has a tensile modulus of elasticity in the range of 5 to 50 kgf / cm ² , because the release layer does not break or crack when the release sheet is formed.

As the electron beam-curable silicone compound,
A silicone resin having a polymerizable double bond such as a vinyl group or an acryl group, which is cured with an electron dose of 5 Mrad or less is preferable because the strength of the base sheet is not reduced. Examples of the electron beam-curable silicone resin having a polymerizable double bond include silicone resins described in JP-B-63-196629. Typical examples thereof include RC-705 and RC-RC manufactured by Gold Schmidt. −
720 and X-62-7213 manufactured by Shin-Etsu Chemical Co., Ltd.
X-62-8010 and the like.

In addition to these, polydimethylsiloxane having no polymerizable double bond can be used, but in this case, an electron dose of 10 Mrad or more is required for curing the resin.

In the present invention, a coating solution containing the above-mentioned electron beam-curable silicone compound is applied and cured by electron beam irradiation to form a release layer. Such a coating liquid preferably does not contain a solvent. If a solvent is contained in the coating liquid, a step of heating and evaporating the solvent is required, and at that time, there is a problem that the sheet is thermally contracted and deformed, which is not preferable.

As a method of such a coating, a conventionally known method can be used. Examples of the coating method include an offset gravure coating method, a gravure roll coating method, a transfer roll coating method, a bar coating method, a doctor blade method, and a reverse roll coating method. Among these, an offset gravure coating method and a transfer roll coating method are preferable, and a coating method using a plurality of coating rolls (for example, five) is preferable.

In the present invention, a release layer is formed by curing an electron beam-curable silicone compound by irradiation with an electron beam. To irradiate an electron beam, an electron beam curing device is used. This type of electron beam curing device is of the “scanning type” that scans the spot-shaped electron beam by the width of the sheet to be processed, has a linear filament, and has a uniform width over the width of the sheet to be processed by the curtain-shaped electron beam. "Curtain type" to irradiate is mentioned. Among them, the “curtain type” in which the dose rate dependence of resin curing is improved and the size of the apparatus is adapted to the object of the present invention is preferable.

Examples of the electron beam accelerator include a Cockloft-Walton type, a bande graph type, a resonance type, an insulating core type, a linear type, a dynacitron type, and a high frequency type.

The energy of these electron beams is in the range of 25 to 2000 keV, especially 100 to 500 keV.
It is preferably in the range of keV.

The thickness of the release layer formed by the above-mentioned method is not particularly limited, but is preferably in the range of 0.1 to 5.0 μm. When the thickness of the release layer is within this range, the releasability is good, and curing can be performed in a short time, which is preferable in production.

[Release Sheet] The release sheet of the present invention is a sheet having good stretchability when heated to a molding temperature, that is, a moldable sheet. It refers to a molding method for obtaining a molded body using a sheet as a starting material, such as molding, thermoforming such as vacuum pressure forming, and compression molding such as press molding. Of these, vacuum forming is preferred.

The molded article obtained from the release sheet in the present invention may be, for example, a tray or a cup. Among these, a tray-like or cup-like shape having a drawing ratio (ratio of the length of the molded body in the vertical or horizontal direction to the depth of the molded body) of 1 or less, more preferably 0.5 or less, is particularly preferable.

[0024]

The present invention will be further described below with reference to examples. The peel strength of the release sheet was measured by the following method.

A polyester pressure-sensitive adhesive tape (Nitto 31B) is adhered to the release layer surface of the release sheet, pressed with a 5 kg pressure roller and maintained for 20 hours, and then the peeling force between the release layer and the pressure-sensitive adhesive tape (unit: g / g) 25 mm) using a tensile tester.

The preferable range of the peel strength is 1 to 1
00 g / 25 mm. If the peel strength is less than 1 g / 25 mm, a sheet or the like laminated on the release layer surface may be peeled off from the release sheet, which is not preferable. Conversely, if the peel strength exceeds 100 g / 25 mm, peeling of the laminated sheet or the like from the release layer surface may become difficult, which is not preferable.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.60 measured in an o-chlorophenol solution at 25 ° C. was melted by an extruder, and extruded on a rotary cooling drum maintained at 25 ° C. to obtain a thickness. An unstretched sheet of 200 μm was obtained. One side of this unstretched sheet is coated with an electron beam-curable silicone compound (RC-705, manufactured by Gold Schmidt) at a thickness of 0.5 μm, and then irradiated with an electron beam having a strength of 5 Mrad to remove the silicone compound. A release sheet was prepared by curing. The peel strength of the release sheet was 18 g / 25 mm.

Example 2 X-62-7216 (manufactured by Shin-Etsu Chemical Co., Ltd.) was used as an electron beam-curable silicone compound.
A mold release sheet was prepared in the same manner as in Example 1 except that an electron beam having an intensity of .mu. The release strength of this release sheet is 5
g / 25 mm.

Example 3 The thickness of the unstretched sheet was 300
A release sheet was prepared in the same manner as in Example 1 except that the thickness was set to μm. The release sheet is heated and softened by a vacuum forming machine and vacuum-formed to form a tray-shaped molded body having a length of 20 mm, a width of 10 mm and a depth of 5 mm (16 pieces are taken out, and the inside of the tray-shaped molded body is a release layer). I got The moldability of this release sheet was good.

Example 4 The thickness of the unstretched sheet was 400
A release sheet was prepared in the same manner as in Example 1 except that the thickness was set to μm. This release sheet is heated and softened by a vacuum forming machine to perform vacuum forming, and is 200 mm long, 100 mm wide,
A 20 mm deep tray-shaped formed body (one piece was taken out, and the inside of the tray-shaped formed body was a release layer) was obtained. The moldability (mold traceability, etc.) of this release sheet was good. Further, when the obtained molded bodies are stacked, the sliding property between the molded bodies is good, and the peeling property when peeling off the lid material after heat sealing the lid material to the molded body is also good. Was. In addition, as a result of cutting out the bottom of the obtained molded body and measuring the peel strength,
It was 32 g / 25 mm.

Comparative Example 1 An unstretched sheet was prepared in the same manner as in Example 1 except that the silicone compound was not applied. The peel strength of this unstretched sheet is 980 g / 25 m
m and a high value.

Comparative Example 2 A heat-curable silicone compound (KS-847H, KS-847H) was used in place of the electron beam-curable silicone compound on an unstretched sheet prepared in the same manner as in Example 1.
Shin-Etsu Chemical Co., Ltd.) 99 parts and curing catalyst (PL-50)
T, Shin-Etsu Chemical Co., Ltd.)
Heat treatment was performed at 150 ° C. for 1 minute. However, during the heat treatment, the unstretched sheet shrinks and deforms, and a release sheet that can be practically used was not obtained.

[0033]

According to the present invention, since a release layer made of an electron beam-curable silicone compound is provided on at least one surface of the polyester sheet, the sheet does not shrink or deform, and has excellent release properties and moldability. A moldable release sheet useful for materials and the like can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08J 7/04 CFD C08J 7/04 CFDZ

Claims (3)

[Claims] 1. A moldable release sheet in which a layer comprising an electron beam-curable silicone compound is provided on at least one side of a polyester sheet. 2. The moldable release sheet according to claim 1, wherein the electron beam-curable silicone compound is a silicone compound comprising a siloxane compound having a vinyl group or an acrylic group. 3. A method for producing a moldable release sheet, in which a coating liquid containing an electron beam-curable silicone compound is applied to at least one surface of a polyester sheet and a layer formed by irradiating an electron beam is provided.