JPH0867861A - Production of cellular tacky tape - Google Patents

Abstract

PURPOSE: To obtain a tacky tape, containing fine and uniform bubbles and good in stability of the bubbles. CONSTITUTION: This method for producing a tacky tape containing bubbles is to mix and heat a hot-melt tacky agent with a foaming agent under pressure, foam the foaming agent and apply the resultant foamed mixture onto a substrate, thereby include the bubbles having 5-30μm bubble diameter in the hot-melt tacky agent layer, apply the mixture to a tape substrate and then quick cool the applied mixture in the method for producing the tacky tape having the hot-melt tacky agent layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an adhesive tape containing fine and uniform bubbles in a hot melt adhesive.

[0002]

2. Description of the Related Art Conventionally, by foaming a foaming agent contained in a hot melt adhesive, the contact area with a rough surface of an adherend is increased, thereby improving the adhesive strength and reducing the amount of adhesive applied. Is being pursued. For example, Japanese Patent Publication No. 60-4
Japanese Patent No. 228 discloses the following bubble-containing adhesive. That is, the gas or the decomposed gas obtained by foaming a foaming agent is supplied with a gear pump at 21.09 kg / c.
After being melted in the adhesive under a high pressure of m ² and extruded, air bubbles are generated in the adhesive by opening to atmospheric pressure, which gradually grows and has a diameter in the range of 0.1 to 0.7 mm. That is, bubbles are formed.

However, since the thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape is usually 100 μm or less, when the bubble diameter is larger than this, no bubbles remain in the pressure-sensitive adhesive and large crater-like pores are formed. There is a problem that the pump pressure becomes unstable because cavitation occurs because the gas is not melted in the gear pump.

Further, even if bubbles having a desired size can be formed in the pressure-sensitive adhesive, there remains a problem that the bubbles disappear with the passage of time. Japanese Patent Publication No. 64-6678 proposes the following measures against the disappearance of the bubbles. That is, a heat-decomposable foaming agent is added to an adhesive based on a thermoplastic elastomer such as styrene-isoprene-styrene block copolymer,
At the same time as coating, or after coating, heat the adhesive to decompose the foaming agent, foam and expand the adhesive layer on the tape support, and then rapidly cool it to reduce the internal pressure inside the bubbles. It improves the stability of bubbles.

However, even in this method, since the adhesive has a large thermoplasticity, the adhesive flows during heating to flow into the bubbles and disappear, or when a porous support such as kraft paper is used. Has a drawback that the adhesive penetrates into the kraft paper, and it is difficult to stably contain fine and uniform bubbles in the adhesive layer.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing fine and uniform bubbles and having good bubble stability.

[0007]

The present invention provides a method for producing a pressure-sensitive adhesive tape having a hot-melt pressure-sensitive adhesive layer, wherein the hot-melt pressure-sensitive adhesive and the foaming agent are mixed and heated under pressure to foam the foaming agent and a base material. 5 to 3 by applying
The present invention relates to a manufacturing method, characterized in that 0 μm bubbles are contained in the hot-melt pressure-sensitive adhesive layer, and the hot-melt pressure-sensitive adhesive layer is coated on a tape substrate and then rapidly cooled.

The present inventors have earnestly studied about various conditions such as mixing time for mixing the pressure-sensitive adhesive and the foaming agent; mixing pressure; mixing temperature based on melting temperature of the pressure-sensitive adhesive and decomposition temperature of the foaming agent. In order to stably contain fine and uniform bubbles in the pressure-sensitive adhesive, it was found that it is an important factor that the pressure-sensitive adhesive and the foaming agent are mixed and heated under pressure to foam, in particular, to complete the present invention. I arrived.

In the present invention, first, the relationship between the tape size such as the bubble diameter in the pressure-sensitive adhesive, the preservability and stability of the foamed state in the pressure-sensitive adhesive, the conformability to the uneven portion of the adherend, and the initial pressure-sensitive adhesiveness is described. Upon investigation, it was found that bubble diameters in the range 5-30 .mu.m provided the best tape properties. Bubble diameter is 30 μm
Above the above range, the bubbles in the pressure-sensitive adhesive easily move in the pressure-sensitive adhesive above the plasticizing temperature of the pressure-sensitive adhesive, and coalescence is repeated to increase the bubble diameter. Eventually, the bubble diameter becomes equal to or larger than the coating thickness of the pressure-sensitive adhesive, the bubbles scatter from the pressure-sensitive adhesive surface, the pressure-sensitive adhesive surface becomes a large crater shape, the pressure-sensitive adhesive surface is inferior in smoothness, and the pressure-sensitive adhesive property is deteriorated. It is not preferable because the number of bubbles in the inside is remarkably reduced or all the bubbles disappear.
On the other hand, when the cell diameter is less than 5 μm, the effect of improving the adhesiveness to rough surface and the initial adhesiveness is small, which is not preferable.

FIG. 1 is a process diagram showing the manufacturing method of the present invention. The pressure-sensitive adhesive main component liquid 2 in the heating / heat-retaining tank 1 is pumped into the extruder 7 by a gear pump 3 and the foaming agent dispersion liquid 5 in the tank 4 is pumped into the extruder 7 by a fixed amount. In the extruder 7, first, the adhesive and the foaming agent are sufficiently mixed and heated in the mixing and heating area 11, and then the foaming agent is decomposed and foamed in the foaming area 12. In order for the decomposition and foaming of the foaming agent to be carried out uniformly and sufficiently, based on the decomposition temperature and decomposition time of the foaming agent used, and the plasticizing temperature of the pressure-sensitive adhesive used,
It is necessary to set the mixing temperature and the mixing pressure in the extruder 7, and the internal volume and the extrusion amount of the extruder 7.

In order to adjust the bubble size in the pressure-sensitive adhesive to 5 to 30 μm, it is important to set the mixing pressure in the extruder 7 among these conditions. The mixing pressure is set to ³ to 15 kg / cm ² , preferably 5 to 10 kg / cm ² . When the mixing pressure is less than 3 kg / cm ² , the pressure inside the bubbles of the gas generated by the thermal decomposition of the foaming agent is higher than the pressure inside the extruder 7, so that the bubbles expand and, as a result, the diameter of the bubbles after coating is 30 to 30 50μ
It becomes large as m, which is not preferable. On the other hand, the mixing pressure is 15 kg
If it exceeds / cm ² , the solubility of the gas generated by the thermal decomposition of the foaming agent in the pressure-sensitive adhesive increases, so no bubbles are formed in the pressure-sensitive adhesive in the extruder 7 and the gas is extruded from the extruder nozzle 8. Bubbles are suddenly formed later. In this case, the extruder 7
Since the pressure difference between the internal pressure and the atmospheric pressure is large, the bubbles are 50μ.
It expands to m or more, and as a result, large crater-like pores are generated on the surface of the pressure-sensitive adhesive and the pressure-sensitive adhesive property is deteriorated.

Further, the melt viscosity of the pressure-sensitive adhesive also influences the adjustment of the cell diameter. That is, when the melt viscosity of the pressure-sensitive adhesive is high, the growth of bubbles is suppressed, and conversely, when the melt viscosity is low, the bubbles grow large and become large. Therefore, it is necessary to adjust the melt viscosity together with the mixing pressure in the extruder 7 so that the bubble diameter is in the range of 5 to 30 μm. The adjustment of the melt viscosity is most effective by adjusting the addition amount of a liquid substance such as process oil and liquid resin.

The pressure-sensitive adhesive thus prepared is applied to one side of the tape substrate to form the pressure-sensitive adhesive layer, but it is preferable to rapidly cool the tape immediately after coating. When the bubbles that have been sufficiently decomposed and foamed in the foaming region 12 of the extruder 7 are discharged from the nozzle 8, the bubbles tend to expand due to a sudden decrease in ambient pressure and the bubble diameter increases. Therefore, by rapidly cooling the tape after coating, the pressure inside the bubbles is reduced, the expansion of the bubbles is prevented, and the bubbles are fixed in the adhesive. The method for rapidly cooling the tape is, for example, a method of bringing the tape base material surface of the tape base material 9 on which the adhesive layer is not formed into contact with the cooling roll 10 or a method in which the adhesive is applied immediately after the adhesive is applied to the tape base material. Examples include a method of blowing cold air on the surface of the agent.
As described above, a pressure-sensitive adhesive tape including a hot-melt pressure-sensitive adhesive layer containing uniform and fine bubbles having a bubble diameter of 5 to 30 μm can be produced.

For the pressure mixing of the hot melt adhesive and the foaming agent dispersion, various continuous mixing devices can be used in addition to the extruder. In any case, the mixing pressure in the mixing device is 3 It should be ~ 15kg / cm ² . The method for applying the pressure-sensitive adhesive is not particularly limited, and a method using a slot die or the like can be used in addition to the method using a nozzle.

The composition of the hot-melt pressure-sensitive adhesive used in the present invention is not particularly limited, and a styrene-isoprene-styrene type block copolymer, a styrene-butadiene-styrene type copolymer or hydrogen of these copolymers is used. The additive is an elastomer, and rosin-based, terpene-based,
Petroleum-based, tackifying resins such as coumarone and indene, naphthene-based and paraffin-based oils, calcium carbonate,
Mixtures of fillers such as magnesium carbonate and antioxidants such as antioxidants and UV absorbers can be used.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Moreover, "part" in the examples represents the number of parts by weight.

Example 1 A base pressure-sensitive adhesive having the following composition was kneaded and melted at 180 ° C. using a heating kneader (manufactured by Moriyama Seisakusho) to prepare a pressure-sensitive adhesive main component liquid, which was placed in a tank heated at 180 ° C. Stored. (A) Styrene-isoprene-styrene block copolymer ^{* 1)} 100 parts (B) Tackifying resin ^{* 2)} 100 parts (C) Process oil ^{* 3)} 20 parts (D) Filler ^{* 4)} 10 parts (E ) Anti-aging agent ^{* 5)} 1 part * 1): Califlex TR1107 (manufactured by Shell Kagaku) (hereinafter referred to as "SIS") * 2): Quinton D100 [manufactured by Nippon Zeon] * 3): Shelf Rex 371N [Shell Chemical Co., Ltd.] * 4): Carbon Cal NS # 100 [Nitto Koka Kogyo Co., Ltd.] * 5): Nonflex EBP [Seiko Chemical Co., Ltd.]

Further, a foaming liquid having the following composition was stirred and mixed at 25 to 30 ° C. to prepare a foaming agent dispersion, which was stored in a tank. (F) Nitroso compound (pyrolysis type foaming agent) ^{* 6)} 1 part (G) Process oil ^{* 7)} 10 parts * 6): Uniform AZ (decomposition temperature 158 ° C) [Otsuka Chemical Co., Ltd.] * 7): Shell Flex 371N [Shell Chemical Co.]

Next, the pressure-sensitive adhesive main component liquid and the foaming agent dispersion liquid obtained as described above were pumped into the extruder at a weight ratio of 100: 5. The pressure in the extruder is 5-10
The extruder capacity and temperature were set so that the pressure was adjusted to be in the range of kg / cm ² , and the heat required for decomposition of the foaming agent was given while the adhesive stayed in the extruder. The non-laminated surface side of the polyethylene laminated kraft paper, the back surface of which was treated with silicone, through the nozzle (width 300 mm) attached to the tip of the extruder, was used to obtain the thus obtained adhesive containing bubbles of 5 to 30 μm. And the thickness of the adhesive layer is about 50 μm
It was coated so as to become, and immediately cooled through a cooling roll at 15 ° C. and wound around a paper tube to obtain an adhesive tape.

Comparative Example 1 The pressure-sensitive adhesive main component liquid and the foaming agent dispersion liquid were mixed at a temperature of 180 ° C. at atmospheric pressure using a stirring tank, and the pressure-sensitive adhesive thus mixed was 2 kg / cm 2. An adhesive tape was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive tape was discharged at a pressure of ² or less.

Comparative Example 2 An adhesive tape was produced in the same manner as in Example 1 except that the foaming agent was not used.

The bubble diameter, bubble density, adhesive bulk specific gravity and ball tack value of the adhesive tapes obtained in Example 1 and Comparative Examples 1 and 2 were measured. In addition, the storability of bubbles and the ability to follow the uneven surface were tested. In addition, these measurements and tests were performed by the following methods.

Bubble diameter The pressure-sensitive adhesive surface of the pressure-sensitive adhesive tape was observed with a microscope (Olympus SZ
The cell diameter was directly measured by taking a photograph.

Number of Air Bubbles The pressure sensitive adhesive surface of the pressure sensitive adhesive tape was observed under the microscope, and the number of bubbles per unit area of the pressure sensitive adhesive was directly measured by photographing.

Adhesive bulk specific gravity was calculated by the following formula.

[0026]

[Equation 1]

Ball Tack Value According to the J. DOW method, a 10 cm long adhesive tape is applied to a stainless steel plate having an inclination angle of 30 ° in an atmosphere of 5 ° C. with the adhesive side facing up, and 10 cm from the upper end of the adhesive tape. From the position, 30 types of steel balls having a diameter of 3/32 to 1 inch were rolled at an initial speed of 0, and the number of the maximum steel ball stopped on the adhesive tape was defined as the ball tack value. The larger the ball tack value, the higher the initial adhesiveness.

Storability of air bubbles After the rolled adhesive tape was stored at a temperature of 50 ° C. for 20 days, it was disentangled and the adhesive surface was observed with a microscope.
The degree of disappearance of bubbles was examined.

Conformity to unevenly adhered surface A water-resistant abrasive paper C-280 is flatly pasted with an adhesive tape of 25 cm in length, and then the abrasive paper with the adhesive tape attached is the outer surface. Thus, it was rolled into a size of 5 cm in diameter and left for 60 minutes. Then, observe the floating state of the tape when it is spread flat.

Table 1 shows the results obtained by the above measurement and test.

[0031]

[Table 1]

Comparative Examples 3 to 6 Mixing of the pressure-sensitive adhesive main component and the foaming agent dispersion was carried out in the same ratio as in Example 1 using a stirring tank at a temperature of 180 ° C. under atmospheric pressure, and in the same manner as in Example 1. It was discharged from a nozzle and coated on a tape base material. Immediately after coating, the back surface of the tape was brought into contact with a cooling roll for cooling, and the adhesive surface was heated with a far infrared heating lamp. Coating speed of 5 m / min (Comparative Example 3),
10 m / min (Comparative Example 4), 20 m / min (Comparative Example 5) and 30
The state of bubbles was observed by setting m / min (Comparative Example 6) and changing the average residence time of the adhesive in the extruder in accordance with the coating speed.

Bubble diameter, number of bubbles, pressure-sensitive adhesive layer thickness after cooling, pressure-sensitive adhesive bulk density, pressure-sensitive adhesive force, ball tack value and probe tack value of the pressure-sensitive adhesive tapes obtained in Example 1 and Comparative Examples 3 to 6. Was measured. In addition, the storability of bubbles and the ability to follow the uneven surface were tested. In addition, among these measuring methods, methods other than the above will be described below.

Adhesion According to JIS Z0237, a 25 mm width adhesive tape was attached to a stainless steel panel in an atmosphere of 23 ° C., and a 2 kg rubber roll was pressure-bonded back and forth once at a speed of 300 mm / min. The peeling force was measured at a peeling speed of 300 mm / min.

Probe tack: According to ASTM D-2979, using an NS probe tack tester (manufactured by Nichiban Co., Ltd.), the diameter of a cylindrical contactor (probe): 5 mm, pressing 100 gf / cm ² , contact time: 1 Second, peeling speed: Tested under the condition of 10 mm / sec.

Table 2 shows the results obtained by the above measurement and test. Table 2 also shows the pressure in the extruder, the average residence time of the adhesive in the extruder, and the coating speed.

[0037]

[Table 2]

The pressure-sensitive adhesive tape obtained in Example 1 contained fine and uniform bubbles of 5 to 30 μm in the pressure-sensitive adhesive.
The stability of bubbles is also excellent, the bulk density of the adhesive is small, and the application amount of the adhesive can be reduced. In addition, the conformability to the uneven surface and the initial tackiness (tack) are good, and the quality is satisfactory. On the other hand, in Comparative Example 1, the bubble diameter is large and its stability is poor. In terms of quality, the ability to follow the uneven surface is insufficient. In Comparative Example 2, since no bubbles are generated, the amount of adhesive applied cannot be reduced. In each of Comparative Examples 3 to 6, the bubble diameter was too large, the stability of the bubble was poor, the amount of the adhesive applied could not be sufficiently reduced, and the quality was not sufficient to follow the uneven adherend surface. It was

[0039]

Industrial Applicability According to the present invention, it becomes possible to manufacture an adhesive tape having a pressure-sensitive adhesive layer containing fine and uniform bubbles and having good bubble stability.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heating / heat-retaining tank 2 ... Adhesive main component liquid 3 ... Gear pump 4 ... Tank 5 ... Foaming agent dispersion liquid 6 ... Metering pump 7 ... Extruder 8 ... Nozzle 9 ... Tape base material 10 ... Cooling roll 11 ... Mixing heating area 12 … Foamed area

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kinnosuke Hino 2-4, 9danminami, Chiyoda-ku, Tokyo Nichiban Co., Ltd. No. 2-4 Nichiban Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a pressure-sensitive adhesive tape comprising a hot-melt pressure-sensitive adhesive layer, wherein the hot-melt pressure-sensitive adhesive and a foaming agent are mixed and heated under pressure to foam the foaming agent and apply it to a substrate to form bubbles. A method for manufacturing, characterized in that air bubbles having a diameter of 5 to 30 μm are contained in the hot melt pressure-sensitive adhesive layer, and the hot melt pressure sensitive adhesive layer is coated on a tape substrate and then rapidly cooled.