JPH0445184A - Tacky adhesion foam sheet and its production - Google Patents

Abstract

PURPOSE:To obtain the title pressure-sensitive sheet suitable for sticking of structure, temporary fixing, etc., by laminating or impregnating a tacky agent to a foam sheet containing both open cells by mechanical stirring and closed cells by a blowing agent. CONSTITUTION:An acrylic emulsion containing an inorganic and/or organic blowing agent is foamed by mechanical stirring to form open cells and the foam is applied in given thickness to the surface of a substrate. Then the foam is heated, dried, closed cells are made by the reaction of the blowing agent contained in the foam to form a foam sheet containing both open cells and closed cells and a tacky agent is laminated or impregnated into the sheet to give the objective sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an adhesive foam sheet and a method for manufacturing the same. More specifically, the present invention relates to a pressure-sensitive adhesive foam sheet suitable for laminating structures, time-fixing, etc., and a method for producing the same.

(Prior art) There are several methods for bonding structures such as metals, metals and plastics, woven fabrics, non-woven fabrics, rubber, etc., such as bonding with adhesives, double-sided adhesive tape, etc., and mechanical bonding with rivets. Among these, bonding using adhesive tape has excellent workability and is widely practiced.

Particularly, as a pressure-sensitive adhesive tape suitable for bonding uneven surfaces, one in which an adhesive layer is provided on a flexible foam sheet as a base material is known (e.g., Japanese Patent Application Laid-Open No. 47-30743). .

The above-mentioned conventional pressure-sensitive adhesive tape uses a urethane foam sheet or a foam sheet made from a synthetic resin such as polyethylene or polyvinyl acetate as its base tape.

However, those using retayu/formsort as the base material have poor weather resistance, gradually become hard and brittle, and the adhesive performance deteriorates.

In addition, for adhesive tapes based on foam sheets made of synthetic resins such as polyethylene and polyvinyl acetate, if sufficient flexibility is given to the tape, the elongation decreases, resulting in a decrease in stress relaxation properties and elongation resistance. It is difficult to find the right balance for adhesion.

Furthermore, since the above-mentioned foam sheets form closed cells, they tend to rebound against minute irregularities on the bonding surface and tend to lift up, reducing adhesive strength, or depending on the characteristics of each major synthetic resin. There is.

In order to solve the above problems, an adhesive sheet using a foam sheet formed from a foam with an open cell structure obtained by mechanically stirring an acrylic emulsion as a base material was proposed (Japanese Patent Laid-Open Publication No. 89585/1989). has been done.

[Problem to be solved by the invention]

However, since the above-mentioned adhesive sheet is based on a foam sheet obtained from a foam with an open cell structure, it is weak against splitting and easily causes delamination, and also has problems such as not being expected to have sufficient water resistance and moisture resistance. have a problem.

In order to solve the various problems mentioned above with conventional adhesive sheets, the present invention uses a foam sheet as a base material in which closed cells formed by the reaction of a blowing agent and open cells formed by mechanical stirring are mixed. The present invention provides an adhesive foam sheet and a method for manufacturing the sheet.

[Means to solve the problem]

The adhesive foam sheet of the present invention is made from an acrylic emulsion containing an inorganic and/or organic blowing agent,
It is characterized by being laminated or impregnated with an adhesive on a foam sheet in which open cells created by mechanical stirring and closed cells created by the reaction of an inorganic and/or organic blowing agent during the heat drying process coexist. .

The manufacturing method for this adhesive foam sort involves foaming an acrylic emulsion containing an inorganic and/or organic blowing agent by mechanical stirring to generate open cells, and then applying the foam with the open cell structure to the surface of the base material as required. A foam sheet with a mixture of open cells and closed cells is created by forming closed cells by the reaction of the blowing agent contained in the open cell foam in the subsequent heat drying process. The foam sheet is laminated or impregnated with an adhesive.

The adhesive foam sheet obtained by the present invention uses an acrylic emulsion containing an inorganic and/or organic blowing agent as a starting material, and consists of open cells formed by mechanical stirring and closed cells formed by the reaction of the blowing agent. This adhesive foam sheet has improved splitting resistance, elongation, water resistance, and moisture resistance.

The above-mentioned open cells are mainly caused by mechanical stirring of the acrylic emulsion, in which gas is taken into the emulsion as bubbles. Any gas may be used as long as it is inert to the acrylic emulsion, and air is a preferable gas both economically and in terms of processing.

Closed cells are mainly formed by gas generated when an inorganic blowing agent or an organic blowing agent is decomposed during the process of heating and drying the emulsion. As a gas,
Although it depends on the type of blowing agent, which will be described later, it is usually nitrogen or carbon dioxide.

The density of the acrylic emulsion foam sheet in the present invention is preferably in the range of 0.1 to 0.8 g/aM. If the density is less than Q, Ig/cffl, problems arise in terms of strength, and desirable physical properties such as split resistance, elongation, water resistance, and moisture resistance, which are the objectives of the present invention, cannot be obtained. Further, if the density exceeds 0.8 g/cJ, flexibility will be lost, which is not preferable.

Conventionally, chemically foamed acrylic emulsion products using foaming agents have had problems in practical application due to lack of shape retention, but the present invention has succeeded in creating foam sheets by mixing chemical foaming and mechanically stirred foaming. This solves the above problem.

The adhesive foam sheet of the present invention is a heat-dried foam of the acrylic emulsion formed into a sheet on a base material such as a film, and is laminated or impregnated with an adhesive, and has an open cell structure. It has a closed cell structure, is flexible and has high elongation, so it follows the irregularities of the adherend and has a large adhesive area, and has excellent basic physical properties necessary for joining structures such as splitting resistance and shear resistance. It also has excellent water resistance and moisture resistance.

Next, a method for manufacturing the adhesive foam sheet, which is another object of the present invention, will be explained.

The acrylic emulsion used in the present invention must have good foaming properties and can contain organic and inorganic foaming agents. In other words, gas can be sufficiently mixed by mechanical stirring,
Moreover, it is desirable that the defoaming rate is slow and the resulting foam has a high viscosity to the extent that it can be coated onto a substrate.

In the present invention, the acrylic emulsion may be used alone, or an appropriate blend of the acrylic emulsion with an emulsion of polyurethane, ethylene vinyl acetate copolymer, synthetic rubber, or the like may be used.

Foam sheets obtained from these emulsions need to have sufficient elongation and elasticity, and it is also necessary to change the flexibility depending on the purpose. As a guideline, methods such as selecting an acrylic emulsion with a low glass transition point (Tg), increasing the cell ratio, or adjusting the amount of blowing agent are used.

When using an acrylic emulsion with a solid content concentration of about 50%, the bubble ratio that can actually be created is 2 to 1 in a wet state.
0 times, and is selected depending on the flexibility required for the final adhesive tape.

Inorganic blowing agents used in the present invention include, for example, sodium hydrogen carbonate, ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrite, etc., and organic blowing agents include, for example, azudicarponamide (AD).
CA), abbisisobutyronitrile (AIBN),
Diazoaminohenzene (DAB), Henzensulfonylhydrazide (BSH), P-toluenesulfonylhydrazide (TSH), etc. may be used.Each of these blowing agents may be used alone, or two types may be used. A mixture of the above may be used.

In addition to the foaming agent, a foam stabilizer and a thickener can be added to adjust the foaming ratio and the like. As the foam stabilizer, for example, ammonium stearate can be used to improve the foaming ratio and stabilize foaming. As a thickener, for example, Rohm and Haas' ASE-6
0 (trade name) is preferably used, and the viscosity can be adjusted to make it easy to apply.

In this way, the desired balance of foam particle size, foaming ratio, and foam viscosity can be achieved by adjusting the amounts of the foam stabilizer and thickener added.

In the present invention, for 100 parts by weight of the acrylic emulsion, 1 to 10.0 parts by weight of a foaming agent and 0.5 to 1 part by weight of a foam stabilizer are used.
The amount of the thickener can be selected and blended in the range of 0.0 parts by weight and 0 to 5.0 parts by weight of the thickener.

The mixture is mechanically stirred using a mixer or the like to incorporate surrounding gas into the emulsion as bubbles to form a foam. Any gas may be used as long as it is inert to the acrylic emulsion, such as air, nitrogen, argon, etc. Among them, air is economically the most preferable. The temperature at this time is preferably room temperature. The bubbles generated in the emulsion by this operation are mainly open bubbles.

After this foam is applied onto the surface of the base material, it is heated and dried to thermally decompose the foaming agent, thereby causing further foaming. The bubbles generated at this time are mainly closed cells.

The base material to which the foam is applied is preferably in the form of a tape or film, and has strength, heat resistance, and releasability, such as polyethylene terephthalate (
PET) film etc. are preferably used.

The foam can be applied by any commonly used method, such as a knife coater, roll coater, etc., to apply the foam to the surface of the base material such as the PET film.

The thickness of the foam to be applied can be arbitrarily selected depending on the intended use of the adhesive foam sheet.
For example, when coating with a knife coater, the clearance between the base material and the knife can be adjusted to form a uniform thickness. Usually, a thickness of 0°1 to 2 mm is preferred.

The foam sheet obtained as described above contains a mixture of open cells produced by mechanical stirring, which is a feature of the present invention, and closed cells produced by thermal decomposition of the blowing agent, and its density is 0.
．． It is in the range of 1 to 0.8 g/C-.

The adhesive foam sheet of the present invention is produced by impregnating or coating the foam sheet with an adhesive.

The adhesive used in the present invention includes various adhesives such as silicone-based, natural rubber-based, synthetic rubber-based, and acrylic-based adhesives. Among these, acrylic pressure-sensitive adhesives are preferred, taking into consideration water resistance, moisture resistance, weather resistance, price, etc. The acrylic adhesive may be a solution polymerization type,
It may also be of emulsion polymerization type.

As a method for impregnating a foam sheet with an adhesive, there is a method, for example, by applying a corresponding amount of adhesive onto the foam sheet and drying it, thereby allowing the adhesive to permeate into the foam sheet.

Further, as a method for laminating and transferring the adhesive to the foam sheet, for example, a method can be used in which the adhesive is applied onto a film having mold releasability, dried, and then pressure-transferred to the foam sheet.

By repeating the same operation on the back side of this foam sheet, a foam sheet with adhesive laminated on both sides can be manufactured.

It is also possible to further apply an adhesive to the material impregnated with the adhesive by the above-described method to provide even more bonding strength.

In addition, the adhesive that is laminated on both the front and back sides of the foam sheet is
In addition to the same adhesive, when the adherends are different or the surface conditions of the adherends are different, different adhesives can be selected taking into consideration the adhesive properties.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 100 parts by weight of acrylic emulsion (Nicadurus 455 manufactured by Nippon Carbide ■), 3 parts by weight of ammonium stearate (foam stabilizer), 1 part by weight of polyvinylpyrrolidone (thickener), and 6 parts by weight of AIBN (foaming agent). oak mixer
The mixture was stirred and mixed to foam. This foam was applied onto a releasable PET film using a knife coater with a clearance of 1.0 mm. 70~110°
The sample was placed in a drying oven (C) for 10 minutes to effect foaming and crosslinking. The resulting foam sheet had a density of 041 g/cj and a thickness of 1.0 mm.

This foam sheet is coated with acrylic adhesive (Soken Chemical Co., Ltd.)
Directly apply the specified amount of SK Dyne 1717).
The adhesive notebook obtained by heating and drying at 70 to 80°C for 3 minutes has a film I of 1.3 mm and a density of 0.82 g/c.
It was d.

Example 2 50 parts by weight of acrylic emulsion (Nicazole 455 manufactured by Nippon Carbide ■), 50 parts by weight of urethane emulsion (Empranyl DCH manufactured by Bayer ■), 3 parts by weight of ammonium stearate (foam stabilizer), polyvinylpyrrolidone (thickener) ) and 5 parts by weight of TSH (foaming agent) were foamed according to Example 1, and the resulting foam was foamed according to Example 1.
It was applied onto a PET film in the same manner as above. This is 70
The density of the foam sheet that was heated and foamed in a drying oven at ~120°C for 10 minutes and crosslinked was 0.45 g/c+d,
The thickness was 1.0 mm.

The film thickness of the adhesive sheet obtained by treating this foam sheet in the same manner as in Example 1 was 1.3 mm, and the density was 0.86 g/
It was cJ.

Example 3 50 parts by weight of acrylic emulsion (Nicasol 455 manufactured by Nippon Carbide ■), 50 parts by weight of ethylene vinyl acetate emulsion (Sumikaflex 500 manufactured by Sumitomo Chemical Co., Ltd.), 3 parts by weight of ammonium stearate (foam stabilizer), polyvinylpyrrolidone ( A foam sheet was prepared in the same manner as in Example 1 using 1 part by weight of thickener), 3 parts by weight of AIBN (foaming agent), and 3 parts by weight of TSH (foaming agent). However, the clearance of the knife coater should be 0.6mm, and the drying temperature should be 70~1.
The temperature was 25°C. The density of the foam sheet thus obtained was 0.31 g/cd, and the thickness was 0.6 mm.

Using this foam sheet, an adhesive sheet obtained in the same manner as in Example 1 had a thickness of 0.73 mm and a density of 0.55.
g/cd.

Comparative Example An adhesive foam sheet with a density of 0.77 g/d and a film thickness of 1.3 mm was prepared in the same manner as in Example 1 except that it did not contain a blowing agent, and its physical properties were compared with that prepared in Example. .

(Results) Foam sheets using an acrylic emulsion containing a blowing agent of the present invention (example product using both mechanical foaming and chemical foaming methods) and an acrylic emulsion containing no foaming agent One side of the adhesive foam sheet, which had acrylic adhesive applied to both sides of the foam sheet (comparative hole fabrication using only mechanical foaming), was coated with non-releasing P.
It was reinforced with an ET film, and the other side was adhered to each substrate listed in Table 1, and the heat resistant tensile strength was compared and the gasoline resistance and water resistance were evaluated (Table 2).

Table 1 conditions: 80°C/30 minutes, 50 m/min Area 25 mm x 25 mm (*... interlayer breakdown) Table 2 conditions: Gasoline resistant immersion 1 hour later, 300 m/min water resistant immersion 1 40 °C / Area after 14 days 251 WIX 25 m [Effects of the invention] The adhesive foam sheet of the present invention is made from an acrylic emulsion containing an inorganic and/or organic blowing agent,
This is because the adhesive is laminated or impregnated on a foam sheet in which open cells generated by mechanical stirring and closed cells generated by the reaction of inorganic and/or organic blowing agents during the heat drying process coexist. It has excellent cohesive strength and has a composite cell structure of open and closed cells, which responds well to the irregularities of the adherend and has a large bonding area. Not only does it have excellent basic physical properties necessary for bonding, but it also has better moisture resistance, solvent resistance, weather resistance, etc. compared to conventional adhesive foam sheets that have a cellular structure consisting mainly of either open cells or closed cells. It's extremely good.

Further, according to the method for producing an adhesive foam sheet of the present invention, foaming by mechanical Pjt stirring and foaming by chemical foaming in the step of coating on a base material and heating and drying are combined. By impregnating or laminating with an adhesive, a new and superior adhesive foam sheet having a composite cell structure can be easily produced.

Claims (2)

[Claims] (1) Made from an acrylic emulsion containing an inorganic and/or organic blowing agent, open cells created by mechanical stirring and closed cells created by the reaction of the inorganic and/or organic blowing agent during the heat drying process coexist. An adhesive foam sheet characterized by a foam sheet laminated or impregnated with an adhesive. (2) An acrylic emulsion containing an inorganic and/or organic blowing agent is foamed by mechanical stirring to generate open cells, and the foam with the open cell structure is applied to the surface of the substrate to the required thickness, and then In the heating and drying process that is carried out, closed cells are generated by the reaction of the blowing agent contained in the open cell foam, thereby forming a foam sheet in which open cells and closed cells are mixed, and the foam sheet has adhesive properties. A method for producing an adhesive foam sheet, characterized by laminating or impregnating it with an agent.