JPH0711581A - Heat-resistant releasing sheet and its production - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant releasing sheet having excellent heat- resistance and release property, free from pinhole and exhibiting high durability and abrasion resistance. CONSTITUTION:This heat-resistant releasing sheet is a woven glass fabric made of glass fibers coated with a layer composed mainly of a silane coupling agent and a layer of a fluororesin, wherein at least one surface of the fabric is laminated with a fluororesin sheet heat-welded to the surface. This heat-resistant releasing sheet is produced by impregnating a silane coupling agent in a woven glass fabric, drying the agent, impregnating a dispersion of a fluororesin, drying the dispersion and laminating a fluororesin sheet to the fabric by heat-welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant release sheet having excellent heat resistance, mold release property, water / oil resistance, and abrasion resistance, which is used as a cooking product for food, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a food release sheet having excellent heat resistance and mold releasability for food applications such as cakes, confectionery such as cookies, meat retort foods such as hamburgers, heat resistance of glass fiber, paper, etc. A fluororesin having excellent releasability as a material, for example, a sheet impregnated with polytetrafluoroethylene or a sheet impregnated with a silicone resin has been used.

[0003]

However, in these conventional techniques, a fluororesin such as polytetrafluoroethylene having excellent heat resistance and releasability is used as a heat resistant fiber by repeating the resin so as to form a dense film. It was impregnated and treated. This technique has a problem in that pinholes are formed on the film surface due to evaporation of water contained in the resin dispersion and thermal decomposition of the surfactant in the drying and firing steps after impregnation. When foods such as hamburgers are heat-treated, pinholes act as anchors, which hinders mold releasability and causes food to stick, which causes charring when used for a long time, and scrapes chars with a rubber spatula. When it is taken, the charcoal is strong and the adhesive force between the sheets is strong, which causes the sheets to break and shorten the service life. In addition, moisture and oils permeate through fine pinholes during heating to promote chemical and thermal deterioration of heat-resistant fibers such as glass fabric inside.

On the other hand, a release sheet having a heat-resistant fiber impregnated with a silicone resin has a limit in heat resistance as compared with a sheet made of a fluororesin composite, has a limited range of application, and has a long life. It was inferior in terms.

As a result of intensive studies to solve the above problems, the present invention has excellent heat resistance and releasability, and has no pinholes. Therefore, a glass fabric made of water or oil exuded from food when heated is used. It is intended to provide a heat-resistant release sheet which is excellent in durability and abrasion resistance without deterioration.

[0006]

The present invention employs the following means in order to solve the above problems. That is, the heat-resistant release sheet of the present invention, at least one surface of the glass woven fabric composed of the glass fiber coated with a layer containing a silane coupling agent as a main component and a fluororesin layer is heat-sealed with the fluororesin sheet. The method for manufacturing such a heat-resistant release sheet,
It is characterized in that a glass woven fabric is impregnated with a silane coupling agent in advance and then dried, then impregnated with a dispersion liquid of a fluororesin and then dried, and a fluororesin sheet is heat-sealed to form a composite.

[0007]

The present invention has been earnestly studied for a release sheet having a glass fiber woven fabric as a base fabric. As a result, by using a silane coupling agent and a fluororesin together, there is no pinhole, and at the same time, heat resistance and release It was made clear that it is possible to provide a release sheet satisfying the properties of excellent durability, wear resistance and durability.

That is, according to the present invention, a glass woven fabric is previously treated with a silane coupling agent having a good affinity with a fluororesin, and then a dispersion of the fluororesin is applied to form a thin layer of the fluororesin on the surface. Further, a fluororesin sheet (film) is attached by heat fusion and integrally molded. By heat-sealing such a fluororesin sheet,
It has been clarified that it is possible to provide an excellent composite sheet that completely eliminates surface smoothness and pinholes, though the number of steps is extremely small compared to the conventional method of only impregnating fluororesin. is there.

The heat-resistant release sheet produced by the present invention is characterized in that it has excellent heat resistance as compared with a sheet impregnated with a silicone resin having relatively good heat resistance. The heat-resistant release sheet improves the adhesiveness between a fluororesin sheet and a silicone layer that imparts an affinity between a glass fabric having excellent heat resistance and a fluororesin, and forms a fluororesin layer and a sheet that imparts abrasion resistance. It is composed of a composite of fluororesin sheets that impart heat resistance, releasability, and water / oil resistance.

The glass fiber used in the present invention is not particularly limited in its type and diameter of single fiber, but the diameter is 10
μ or less is useful for obtaining high strength, especially considering the versatility when used as the heat-resistant release sheet of the present invention,
From the viewpoint of cost, a material having a size of 4 to 8 μ is mainly used.

The structure of the woven fabric used in the present invention is not particularly limited, but a plain weave is preferably used because it is necessary to make it smooth in order to improve the adhesion to foods. The glass fabric used in the present invention contains γ- (2-aminoethyl) aminopropylmethyldimethoxysilane and γ-glycidoxypropyltrimethoxysilane in order to improve the affinity with the fluororesin in the subsequent step. , Γ-methacryloxypropyltrimethoxysilane, n- (trimethoxysilylpropyl) ethylenediamine, tridecafluorooxyltriethoxysilane and the like are applied in advance. In addition, when it is desired to impart flexibility to the woven fabric, the silane coupling agent may be SF8417, SF8411, SF8413, BY-16-83 manufactured by Toray Dow Corning Silicone Co., Ltd.
9, it is preferable to blend a softening agent such as SH-8400, BY-22-819, and SM8701.

Usually, in the impregnation step, it is preferable to use a continuous coating and heating device comprising an impregnating device provided with a squeezing roller or a rod coater for adjusting the amount of adhesion in the impregnating tank and a heating zone. In the heating zone, pretreatment of the silane coupling agent and the softening agent and drying after impregnation with the fluororesin are performed. In this drying, further firing can be performed if necessary.

The fluororesin layer coated on the silicone layer is a tetrafluoroethylene polymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-polymer.
At least one resin selected from perfluoroalkyl vinyl ether copolymers is used.

Examples of the water dispersion used for impregnating the above-mentioned fluororesin include "Polyflon D-2", "Polyflon D-1" and "Polyflon D-2" manufactured by Daikin Industries, Ltd.
C ”,“ Neotron AD-2CR ”,“ Neotron ND-1 ”, and“ Teflon ”manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.
It can be formed by coating with 30-J "or the like. The fluororesin aqueous dispersion is coated and then dried, and the drying temperature is in the range of 90 to 200 ° C. Also, if necessary, if you want to bake, 25
Firing conditions in the range of 0 to 420 ° C. are desirable. If the temperature exceeds 420 ° C., the strength of the glass fiber tends to decrease greatly due to the heat treatment. Regarding the film thickness of the fluororesin layer to be applied, it is only necessary to secure the minimum necessary amount for the heat-adhesion of the fluororesin sheet to be heat-bonded next, and it is sufficient that it can be applied uniformly on the surface of the glass fiber. The film thickness of the fluororesin layer is preferably 50 μm or less in view of the above and thermal conductivity.

Next, the kind and thickness of the fluororesin sheet to be heat-sealed differ depending on the purpose and are selected mainly according to the required heat resistance and thermal conductivity. It is preferably used from the aspect.

Examples of the fluororesin sheet used in the present invention include tetrafluoroethylene polymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer and tetrafluoroethylene. -Use is made of at least one resin selected from perfluoroalkyl vinyl ether copolymers. A pigment such as carbon, titanium oxide, alumina, zirconium oxide or the like may be previously blended in the fluororesin sheet of the present invention in order to identify the color and impart thermal conductivity.

In order to heat-bond such a fluororesin sheet, it is pressure-bonded by a pressure-bonding device such as a press, a calender roll or a double belt press, and heat-treated. Although the heat fusion temperature depends on the pressure bonding time, it is desirable to select a temperature condition of melting point to melting point + 70 ° C. based on the melting point of the fluororesin sheet.

As a pretreatment method for heat fusion, application of the above-mentioned fluororesin dispersion having good affinity facilitates heat adhesion of the fluororesin sheet. In this case, it is preferable to apply the same component as that of the fluororesin sheet to be heat-sealed later or a fluororesin having a low melting point, because it facilitates the heat-fusion later. Further, it is effective to enhance affinity between the resins by subjecting the surface of the fluororesin sheet to plasma or corona discharge treatment. In this case, heat fusion can be performed at a temperature equal to or lower than the melting point of the fluororesin sheet.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Glass fabric manufactured by Nitto Boseki Co., Ltd. WE106 104 (mass: 25 g / m ² , thickness: 30 μm, which has been pre-sized)
Woven structure: plain weave, weave density (vertical x horizontal): 56 x 56 /
25 mm) is heat treated under the condition of 360 ° C. × 10 min,
The surface sizing agent was removed. Then, γ- (2-aminoethyl) was added to this glass fabric as a coupling agent.
It was impregnated with a 1.0% aqueous solution of aminopropylmethyldimethoxysilane, and then dried under a heat treatment condition of 110 ° C. for 5 minutes.

Further, a dispersion liquid of tetrafluoroethylene-ethylene copolymer (manufactured by Daikin Industries, Ltd. "ND
-1 ") impregnated and squeezed with mangle, then 110 ° C
It was dried under the condition of 5 minutes and then heat-treated and sintered under the condition of 300 ° C. × 10 minutes. Next, both sides of this sintered glass fabric were sandwiched with two 20 μm tetrafluoroethylene-hexafluoropropylene copolymer films, and 2
A heat-resistant release sheet having a thickness of 68 μm was obtained by heat-sealing with a heating press at 80 ° C. for 5 minutes under a pressure of 75 kg / cm ² and bonding.

Comparative Example 1 Under the same conditions as in Example 1 except that the impregnation step of the dispersion liquid of tetrafluoroethylene-hexafluoropropylene copolymer ("ND-1" manufactured by Daikin Industries, Ltd.) was omitted. A composite sheet having a thickness of 65 μm was produced. The abrasion resistance of the sheets obtained in Example 1 and Comparative Example 1 was evaluated using a Scott type rubbing resistance tester. The measurement conditions were a load of 500 g and a rubbing count of 5000 times. As a result, the sheet treated with the dispersion of the tetrafluoroethylene-ethylene copolymer before heat-sealing the film of the tetrafluoroethylene-ethylene copolymer had no peeling of the sheet even after the rubbing test. On the other hand, the untreated product showed delamination between the glass fabric and the film layer. From this, it was confirmed that the pretreatment with the dispersion liquid of tetrafluoroethylene-ethylene copolymer was effective for improving the wear resistance.

Comparative Example 2 Glass fabric WE106 104 (mass: 25 g / m ² , thickness: 30 μ, manufactured by Nitto Boseki Co., Ltd., which has been pre-sized.
Woven structure: plain weave, weave density (vertical x horizontal): 56 x 56 /
25 mm) was heat-treated under the conditions of 360 ° C. for 10 minutes to remove the sizing agent on the surface. Then, as a coupling agent, a 1.0% aqueous solution of γ- (2-aminoethyl) aminopropylmethyldimethoxysilane was impregnated, and 110
It was dried under a heat treatment condition of ℃ × 5 minutes. Next, a dispersion of polytetrafluoroethylene ("D-2" manufactured by Daikin Industries, Ltd.) was impregnated into the glass fabric treated with the above coupling agent,
After squeezing with a mangle, heat treatment at 110 ° C x 5 minutes is performed to dry, and then 380 ° C x 1 for sintering.
Heat treatment was performed for 0 minutes. In order to secure the required film thickness, the same impregnation, drying and firing were performed three times, and a fluororesin was applied to the glass fabric to obtain a 70 μm-thick thin sheet.

Example 2 Using the same glass fabric and coupling agent as in Comparative Example 2, a glass fabric was impregnated with a coupling agent under the same conditions as in Comparative Example 2 and dried. Next, after impregnating the dispersion liquid of polytetrafluoroethylene ("D-2" manufactured by Daikin Industries, Ltd.) and pressing with a mangle, it is heat-treated at 110 ° C for 5 minutes and dried, and then sintered. In order to carry out, heat treatment was applied at 380 ° C. for 10 minutes. Next, two 20 μm polytetrafluoroethylene films were sandwiched between the above-mentioned pretreated glass fabrics, and heat fusion was performed using a heat press machine under a pressure condition of 380 ° C. × 5 minutes and 75 kg / cm ^2. And pasted together to obtain a heat-resistant release sheet having a thickness of 68 μm.

The sheets obtained in Comparative Example 2 and Example 2 were subjected to tensile strength (JIS-3420) and releasability, and the surface of the sheet was observed by an electron microscope (magnification: 3000 times). The results are shown in Table 1. As for the releasability of the sheet, the sheet was set on a hot plate of a grill, a retort hamburger was placed on the sheet, heat treated at 200 ° C. for 50 seconds, and then baked out. This operation was repeated 100 times, and the area of the burnt substance adhered to the surface of the sheet and the amount of the burnt substance were visually compared and observed.

From Table 1, as compared with the impregnation method of Comparative Example 1, Example 1 of the present invention has a smooth surface and has no pinholes, so there is little sticking of charring and good releasability. .
Also, it can be seen that the tensile strength is high because the heat history in the manufacturing process is small. Furthermore, the deterioration of the glass fabric after use is small and the strength of the sheet is not significantly reduced.

Comparative Example 3 Glass fabric WE108 104 (mass: 48 g / m ² , thickness: 60 μ, manufactured by Nitto Boseki Co., Ltd., which has been pre-sized.
Woven structure: plain weave, weave density (vertical x horizontal): 60 x 46 /
25 mm) was heat-treated under the conditions of 360 ° C. for 10 minutes to remove the sizing agent on the surface. Then, as a coupling agent, a 1.0% aqueous solution of γ- (2-aminoethyl) aminopropylmethyldimethoxysilane was impregnated, and 110
It was dried under a heat treatment condition of ℃ × 5 minutes. Next, a dispersion liquid of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (“Neoflon AD-2C manufactured by Daikin Industries, Ltd.
R ″) is impregnated into the glass fabric treated with the above-mentioned coupling agent, squeezed with a mangle, then heat-treated at 110 ° C. for 5 minutes to be dried, and then sintered for sintering.
Heat treatment was performed at 0 ° C. for 10 minutes. The same impregnation, drying and firing were performed three times to secure the required film thickness, and a fluorocarbon resin was applied to the glass fabric to obtain a 100 μ-thick composite sheet.

Example 3 Using the same glass fabric and the same coupling agent as in Comparative Example 3, the glass fabric was impregnated with the coupling agent in the same manner as in Comparative Example 3 and dried. Next, after impregnating with a dispersion liquid of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (“Neotron AD-2CR” manufactured by Daikin Industries, Ltd.) and squeezing with a mangle, the condition is 110 ° C. × 5 minutes. It was dried and then subjected to heat treatment at 350 ° C. for 10 minutes for sintering. Then, two 20 μm tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer films were sandwiched between the above pretreated glass fabrics, 340 ° C. × 5 minutes, 7
Using a heating press machine under a pressurizing condition of 5 kg / cm ² , heat fusion was performed and bonding was performed to obtain a 100 μm-thick thin sheet. Regarding the film materials obtained in Comparative Example 3 and Example 3, the tensile strength (J
IS-3420), releasability, and the surface of the sheet were observed with an electron microscope (magnification: 3000 times). The results are shown in Table 1. Table 1
Therefore, as compared with Comparative Example 3, Example 3 had a smooth surface and had no pinholes. Therefore, the adhesion of scorching was small and the releasability was good. Further, since the heat history in the manufacturing process is small, a material having high tensile strength was obtained. Furthermore, it was confirmed that the deterioration of the glass fabric after use was small and the strength of the sheet was not significantly reduced.

Comparative Example 4 The same glass fabric and the same coupling agent as in Comparative Example 3 were used to prepare a glass fabric under the same impregnation and drying conditions as in Comparative Example 3. Next, the solid content 3 dissolved in xylene
5% "S" made by Toray Dow Corning Silicone Co., Ltd.
E9140 "silicone resin is applied by rollover knife coating and cured at 25 ℃ for 24 hours.
A 98μ sheet made of silicone resin was obtained. The sheet was subjected to tensile strength (JIS-3420) and releasability, and the surface of the sheet was observed with an electron microscope (magnification: 3000 times). The results are shown in Table 1.

Comparative Example 4 has a small heat history in the manufacturing process,
Therefore, the strength is small, the surface is relatively smooth, and there are few pinholes, but since the affinity with the oil component exuding from the hamburger is good, the releasability is poor and there are many charring. Example 2 of the present invention has a smoother surface and excellent releasability as compared with the sheet made of the silicone resin shown in Comparative Example 4.

[0030]

[Table 1]

[0031]

The present invention is intended to provide a heat-resistant release sheet which has excellent heat resistance and releasability, has no pinhole, and is excellent in durability and abrasion resistance.

Claims (4)

[Claims] 1. A glass fabric made of glass fibers coated with a layer mainly containing a silane coupling agent and a fluororesin layer, at least one side of which is heat-sealed with a fluororesin sheet. Heat-resistant release sheet that does. 2. A glass fabric is preliminarily impregnated with a silane coupling agent and then dried, then impregnated with a dispersion liquid of a fluororesin and then dried, and a fluororesin sheet is heat-sealed to form a composite. Heat-resistant release sheet manufacturing method. 3. A fluororesin dispersion liquid is at least one selected from a tetrafluoroethylene polymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The heat-resistant release sheet manufacturing method according to claim 1, wherein the heat-resistant release sheet is composed of the resin. 4. The fluororesin sheet comprises a tetrafluoroethylene polymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a tetrafluoroethylene-ethylene copolymer and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The method for producing a heat-resistant release sheet according to claim 1, wherein the heat-resistant release sheet is composed of at least one resin selected from polymers.