JPH0517729A - Adhesive tape - Google Patents

Abstract

PURPOSE:To provide an adhesive tape suitable for using by application on a heat-scaling machine, causing no wrinkle transfer on object articles for heat sealing. CONSTITUTION:For a conventional adhesive tape with a tacky agent layer on the surface of a substrate, there has been such a trouble that when it is applied on a heat-sealing machine, wrinkles develop in a short time and these wrinkles are transferred on an object article. The present tape can resolve this problem by putting a rubbery elastic layer between a substrate and tacky agent layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive tape suitable for use in heat-sealing work of various articles.

[0002]

2. Description of the Related Art A so-called "heat seal", in which a packaging material is heat-sealed, is often used for packaging foods such as confectionery and pickles. In addition, heat sealing may be adopted even when an iron product is wrapped with a rust preventive film.

In heat sealing, as shown in FIG. 1, a heating element 3 is arranged on a metal core 1 with an insulator 2 interposed between the heating element 3 and one side of a heat resistant substrate. Using a device having a heat generating element having a structure in which an adhesive tape 4 provided with a layer is adhered and a pressing element (not shown) arranged above the heat generating element at a predetermined interval, a plastic containing food etc. is used. The bag is set between the heat generating element and the pressing element, and then the heating element is energized to generate heat and the pressing element is pressed against the heat generating element to fuse and seal the opening of the bag. As the pressing element, a core body to which the same adhesive tape as that described above is attached can be used. In addition, the heating element may be built in the core, and in this case also, an adhesive tape is attached to the core.

The pressure-sensitive adhesive tape which is used by being attached to the above-mentioned heat generating element or pressing element is for preventing the molten plastic from being fused to these elements at the time of heat sealing, and has releasability from the molten plastic. A heat-resistant substrate provided with an adhesive layer on one side is used.

[0005]

By the way, when the heat-sealing work is repeated using such an adhesive tape, the tape partially floats from the heat-generating element and the width direction of the element (arrow A in FIG. 1). There is a problem that "wrinkles" occur along the (direction), and these wrinkles are transferred to the corresponding portions of the plastic bag to be heat-sealed, resulting in poor appearance, and there is also a risk of incomplete sealing. It has been confirmed that the wrinkles frequently occur near the central portion in the lengthwise direction of the heat generating element (the direction orthogonal to the arrow A in FIG. 1) and are rare near both ends in the lengthwise direction.

It is considered that the wrinkles are mainly caused by the difference in the coefficient of thermal expansion between the core and the adhesive tape adhered on the core. The core and adhesive tape repeat expansion and contraction by being heated by energization and cooled by stopping them, but due to the difference in thermal expansion coefficient between them (the core is usually a metal, the thermal expansion coefficient is better than that of adhesive tape). It is considered that there is a difference in the degree of expansion and contraction, which appears as peeling at the interface between the two, and this peeled portion becomes wrinkled.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above problems of the prior art, the present inventor has found that a specific intermediate layer is interposed between the base material and the pressure-sensitive adhesive layer.
The inventors have found that it is possible to effectively prevent the generation of wrinkles during heat sealing work, and have completed the present invention.

That is, the adhesive tape according to the present invention comprises an adhesive layer provided on the surface of a fluorine-based substrate via a rubber elastic layer.

Specific examples of the fluorine-based base material used in the present invention include polytetrafluoroethylene (PTF).
Examples thereof include a film made of a fluororesin such as E) or a sheet obtained by impregnating a heat-resistant cloth material with a fluororesin.

As the heat resistant cloth material, a woven cloth made of glass fiber, asbestos fiber, alumina fiber, boron fiber, boron nitride fiber, inorganic fiber such as silicon carbide fiber, titania fiber, and organic fiber such as aromatic polyamide fiber. ,
Alternatively, a non-woven fabric can be used.

In order to obtain a fluorine-based substrate by impregnating such a heat-resistant cloth material with a fluororesin, for example, (a) the heat-resistant cloth material is immersed in a fluororesin dispersion and pulled up,
Then, a method of heating at a temperature equal to or higher than the melting point of the fluororesin (if desired, repeating immersion and heating), (b) spray coating a fluororesin dispersion on the heat-resistant cloth, and then at a temperature equal to or higher than the melting point of the fluororesin. It can be carried out by a method of heating (repeating application and heating if desired), (c) a method of superposing a fluororesin sheet on a heat-resistant cloth material and heating at a temperature equal to or higher than the melting point of the fluororesin. According to these methods, the heat-resistant cloth material is impregnated with the fluororesin and the fluororesin layer is formed on the surface of the cloth material.

In the present invention, a pressure-sensitive adhesive layer is provided on the surface of the above-mentioned fluorine-based substrate via a rubber elastic layer. The rubber elastic layer is made of silicone rubber, nitrile rubber,
It can be formed of rubber such as epichlorohydrin rubber, but silicone rubber is preferable from the viewpoint of heat resistance.
In the present invention, the elastic modulus of this rubber elastic body is 1
When it is set in the range of 0 to 1000 g / mm ^2, the effect of preventing wrinkles during the heat-sealing work becomes particularly excellent. The thickness of the rubber elastic body is not limited, but is usually about 5 to 100 μm.

To provide a rubber elastic layer on the surface of a fluorine-based base material, rubber is dissolved in a solvent such as toluene, xylene, methyl ethyl ketone, acetone, perchloroethylene or chlorobenzene, and this is applied to the surface of the base material. Then, the solvent is removed by heating.

In order to improve the adhesion of the rubber elastic body to the surface of the fluorine-based base material, the surface of the base material may be subjected to a conventional adhesion treatment such as alkali treatment or sputter etching treatment. The alkali treatment is carried out by bringing the surface to be treated of the base material into contact with an alkali metal such as sodium metal in a mixed solution of naphthalene and tetrahydrofuran or in a liquid ammonia. The liquid used for this treatment is commercially available, for example, as “Tetra Etch (trade name, manufactured by Junkosha Co., Ltd.)”, and thus it can be used. In the sputter etching process, a high-frequency voltage is applied between the negative and positive electrodes in a pressure-resistant container under a reduced pressure atmosphere condition to accelerate the cations generated by the discharge in the cathode dark part where the ion energy in the discharge region is large, and It is intended to collide with an article made of fluororesin. Regarding this sputter etching process and the equipment used for this, see Japanese Patent Publication No. 53-22.
108, Japanese Patent Publication No. 56-1337, Japanese Patent Publication No. 5
It is described in detail in Japanese Patent Publication No. 6-1340.

It is not always clear why the provision of this rubber elastic body layer provides the wrinkle prevention effect at the time of heat sealing, but the rubber elastic body easily follows the thermal expansion and contraction of the core in the heating element. It is inferred to be possible.

Further, in the present invention, an adhesive layer (thickness is usually about 5 to 100 μm) is provided on the surface of the rubber elastic layer. The material for the pressure-sensitive adhesive layer is not particularly limited, and those conventionally used as pressure-sensitive adhesives for pressure-sensitive adhesive tapes such as acrylic, rubber, and silicone can be used, but from the viewpoint of heat resistance, silicone It is preferably formed by an adhesive.

Further, in the present invention, at least one of the rubber elastic layer and the pressure-sensitive adhesive layer may contain a heat conductive powder. As the heat conductive powder, for example, metal powder such as iron, aluminum, stainless steel, copper, or metal oxide powder can be used. These have a particle size of about 10 μm or less, and about 10 μm in the rubber elastic layer or the adhesive layer.
It is preferable that the content is contained in an amount of 1000 parts by weight. Due to the inclusion of this heat conductive powder, the heat conduction during the heat sealing work becomes good and the working speed is improved.

The pressure-sensitive adhesive tape according to the present invention can be used by being attached to the heating element of the heat-sealing machine as in the conventional product.

[0019]

Since the present invention is constructed as described above and the rubber elastic body is interposed, it is possible to provide an adhesive tape with less wrinkles during heat sealing work, and to perform the heat sealing work reliably and quickly. it can.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 A glass cloth having a thickness of 70 μm and a basis weight of 65 g / m ² was PT
It is immersed in an aqueous dispersion having an FE concentration of 5% by weight, pulled up, and heated at a temperature of 380 ° C. for 3 minutes. This dipping and heating are repeated three more times to obtain a PTFE impregnation amount of 1
A fluorine-based base material of 10 g / m ² is obtained.

After subjecting one side of this fluorine-based material to alkali treatment, a toluene solution of a two-component type silicone rubber having a molecular weight of 500,000 (rubber concentration 40% by weight) is applied to the treated surface at a temperature of 150 ° C. By heating for 30 minutes,
A silicone rubber layer having a thickness of 30 μm and an elastic modulus of 250 g / mm ² is formed.

Next, a commercially available silicone pressure-sensitive adhesive solution (however, silicone resin 10
(1 part by weight of benzoyl peroxide is added to 0 part by weight), and the silicone resin is crosslinked by removing the solvent by heating at a temperature of 150 ° C. for 10 minutes to form a pressure-sensitive adhesive layer having a thickness of 20 μm. The formed adhesive tape was obtained.

Example 2 200 parts by weight of an aluminum powder having a particle size of 1 μm was mixed with 100 parts by weight of a silicone rubber, and a toluene solution containing 20% by weight of the solid content was used to form a silicone rubber layer containing an aluminum powder. An adhesive tape was obtained in the same manner as in Example 1 except that the adhesive tape was formed.

Example 3 One side of a 100 μm thick PTFE film is treated with alkali. And 100 of silicone rubber with a molecular weight of 300,000
A toluene solution (rubber concentration 20% by weight) containing 2 parts by weight of benzoyl peroxide was applied to the treated surface and heated at 150 ° C. for 20 minutes to give a thickness of 40 μm.
A silicone rubber layer having an elastic modulus of 50 g / mm ² is formed.
Next, in the same manner as in Example 1, a 25 μm thick silicone-based pressure-sensitive adhesive layer was formed on the silicone rubber layer to obtain an adhesive tape.

Example 4 An aluminum powder-containing silicone rubber layer is formed on one side of a fluorine-containing base material in the same manner as in Example 2. Next, on this silicone rubber layer, a toluene solution (solid content concentration 20% by weight) in which 50 parts by weight of aluminum powder (particle size 1 μm) and 1 part by weight of benzoyl peroxide were mixed with 100 parts by weight of silicone resin was applied. Then, it was heated at 170 ° C. for 5 minutes to form a silicone-based pressure-sensitive adhesive layer having a thickness of 20 μm to obtain an adhesive tape.

Comparative Example An adhesive tape was obtained in the same manner as in Example 1 except that the silicone rubber layer was not formed and the thickness of the adhesive layer was 50 μm.

Test Example 1 The pressure-sensitive adhesive tapes of Examples and Comparative Examples were attached to the heating element and pressing element of a commercially available heat sealing machine (FA-300-10 manufactured by Fuji Impulse Co., Ltd.), and the heating time was 0.5 seconds. A polyethylene bag having a thickness of 50 μm was continuously sealed under the condition that the cooling time was 1 second. Both the heating element and the pressing element are made of iron.

In the comparative example, wrinkles were generated on the adhesive tape adhered to the heating element after heat sealing was performed about 1000 times, but in Examples 1 to 4, wrinkles were not observed even after about 5000 times.

Test Example 2 The pressure-sensitive adhesive tapes of Example 2 and Comparative Example were attached to an iron plate at a temperature of 200 ° C., and the temperature rise was measured by a temperature sensor arranged on the tape surface. The obtained results are shown in FIG. 2 as curves a (Example 2) and b (Comparative Example). As shown in FIG. 2, the tape of Example 2 in which the silicone rubber layer contained aluminum powder, which is a heat conductive powder, had a high temperature rising rate and excellent heat conductivity.

[Brief description of drawings]

FIG. 1 is a front view showing an actual example of a heat generating element used for heat sealing.

FIG. 2 is a graph showing the heat conduction performance of the present invention and the conventional adhesive tape.

[Explanation of symbols]

1 core 3 heating element material 4 adhesive tape

Claims (3)

[Claims] 1. A pressure-sensitive adhesive tape comprising a fluorine-based base material, and a pressure-sensitive adhesive layer provided on the surface of the base material via a rubber elastic layer. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the rubber elastic layer and / or the pressure-sensitive adhesive layer contains a heat conductive powder. 3. The pressure-sensitive adhesive tape according to claim 1, wherein the fluorine-based base material is a sheet formed by impregnating a heat-resistant cloth material with a fluororesin.