JPH07119392B2 - Method for manufacturing breathable adhesive tape or sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a breathable pressure-sensitive adhesive tape or sheet used for medical purposes and other purposes.

[Prior Art] Conventionally, medical adhesive products such as adhesive bandages are used by directly adhering to the human body, but if left untouched for a long time,
Itching and rashes occur because the evaporation of water from the surface of the skin is blocked. In order to prevent this, it is effective to make the pasted product breathable. Therefore, many attempts have been made in the past to make the pasted product breathable.

As a new example among them, for example, an organic solvent solution of an adhesive is applied to the surface of a peelable sheet to form an adhesive solution layer, and then the adhesive solution layer is dried while the adhesive solution layer is in an undried state. A method is known in which fine water droplets are sprayed on the surface of the layer and then dried to form a dry pressure-sensitive adhesive layer having fine pores, and the layer is transferred to a breathable substrate (Japanese Patent Laid-Open No. HEI 2).
-213352 gazette). According to this method, water droplets sprayed on the surface of the pressure-sensitive adhesive solution layer while it is in an undried state sinks into the pressure-sensitive adhesive layer, whereby a relatively macro non-uniform portion (pressure-sensitive adhesive) is formed in the pressure-sensitive adhesive layer. Is formed), and the water is evaporated by the subsequent drying, and the organic solvent is evaporated to increase the viscosity of the pressure-sensitive adhesive solution, whereby fine vent holes are formed in the part where water is present. This method is drawing attention as a relatively simple method.

[Problems to be Solved by the Invention] However, the above method has a problem in that the breathable pressure-sensitive adhesive tapes or sheets produced have variations in breathability, and those which do not have desired breathability can be produced.

Then, as a result of various experiments and researches conducted by the present inventors to find out the cause of the above-mentioned problems, the evaporation of water is carried out faster than the evaporation of the organic solvent in the drying step of the above method. It was found that the above problem occurs when water disappears before the viscosity of the solution increases.

An object of the present invention is to solve the above problems and to provide a method capable of producing a breathable pressure-sensitive adhesive tape or sheet having excellent breathability and having uniform breathability.

[Means for Solving the Problems] The method for producing a breathable pressure-sensitive adhesive tape or sheet according to the present invention comprises applying an organic solvent solution of a pressure-sensitive adhesive to the surface of a peelable sheet to form a pressure-sensitive adhesive solution layer, and then forming a pressure-sensitive adhesive solution. While the layer is in an undried state, water droplets are sprayed on the surface of the pressure-sensitive adhesive solution layer and then dried, and then the obtained dry pressure-sensitive adhesive layer is laminated on a breathable substrate to provide breathability. The method for producing an adhesive tape or sheet is characterized in that hot air having a temperature of 60 ° C. or more and a wind speed of 10 m / sec or less is blown onto the surface of the adhesive solution layer for 10 seconds or more at the initial stage of the drying.

First, the principle of forming a dry pressure-sensitive adhesive layer having fine holes on a peelable sheet in the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 schematically shows the process for forming a dry pressure-sensitive adhesive layer having fine pores in the method of the present invention. In FIG.
After forming the pressure-sensitive adhesive solution layer on the surface of the peelable sheet (1) by the roll coater (10), the spray gun (11) is applied to the surface of the pressure-sensitive adhesive solution layer while the pressure-sensitive adhesive solution layer is in an undried state. To disperse water droplets, then send it into the drying device (12), perform initial drying in the initial drying section (12a), and then perform late drying in the latter drying section (12b) to form fine pores. A dry adhesive layer having is obtained. Changes in the pressure-sensitive adhesive solution layer and the pressure-sensitive adhesive layer at this time are shown in FIG. When water droplets are sprayed onto the surface of the pressure-sensitive adhesive solution layer (2) while the pressure-sensitive adhesive solution layer (2) formed on the surface of the peelable sheet (1) is in an undried state, the result is shown in FIG. As shown, the adhered water drops (3) sink into the pressure-sensitive adhesive solution layer (2), thereby forming fine recesses (4) on the surface of the pressure-sensitive adhesive solution layer (2). Next, when initial drying is performed in the initial drying section (12a) of the drying device (12), both water and solvent evaporate, and as shown in FIG. 2 (b), only water is evaporated. Since the water droplets (3) become smaller, the adhesive flows and the recesses (4) become slightly smaller. At this time, the thickness of the adhesive solution layer (2) also becomes thin. Then, when water evaporation progresses in the latter drying section (12b), as shown in FIG. 2 (c), the remaining water droplets (3) become smaller than the recesses (4), but the evaporation of the solvent also progresses and sticks. Since the viscosity of the agent increases, the pressure-sensitive adhesive does not flow and the pressure-sensitive adhesive layer (2A) in an intermediate state can be obtained. The thickness of the adhesive layer (2A) in the intermediate state becomes thinner than that shown in FIG. 2 (b). Furthermore, as the water and solvent evaporate in the late drying section (12b), the adhesive layer (2A) contracts and the recess (4) expands, as shown in FIGS. 2 (d) and (e). At the same time, the water is completely evaporated. Even after that, the solvent continues to evaporate and the shrinkage of the pressure-sensitive adhesive layer (2A) proceeds, and as shown in FIG. 2 (f), the bottom of the recess (4) is torn to form a fine hole (5). At the same time, the viscosity of the pressure-sensitive adhesive is increased to a desired viscosity. In this way, a dry adhesive layer (2B) having fine holes (5) is formed.

In the above, the reason for limiting the initial conditions in the drying step as described above is as follows. Hot air temperature is 60 ℃
This is because both the water and the organic solvent are less likely to evaporate when the hot air blowing time is less than 10 seconds. The upper limits of temperature and spraying time are preferably about 140 ° C. and 120 seconds, respectively. This is because the effect of evaporating water and the organic solvent does not change much even if it exceeds these, extra energy for increasing the temperature is required, and the manufacturing time is long and the cost is high. Especially, the temperature of hot air is 80-120 ℃, and the blowing time is 30
It is preferably within the range of up to 60 seconds. Also,
This is because when the velocity of the hot air exceeds 10 m / sec, the evaporation of water is completed before the organic solvent evaporates and the viscosity of the pressure-sensitive adhesive solution layer increases. This is a state in which there are no water droplets in FIG. 2 (b). In this state, when the pressure-sensitive adhesive flows, the recess formed by water droplets sinking on the surface of the pressure-sensitive adhesive solution layer disappears and the surface of the pressure-sensitive adhesive solution layer becomes smooth (see FIG. 2 (b ) See the chain line (X)), and even if the evaporation of the organic solvent proceeds thereafter, no holes are formed in the pressure-sensitive adhesive layer. Particularly, the wind speed of the hot air is preferably in the range of 0.5 to 2 m / sec. It is preferable that the viscosity of the pressure-sensitive adhesive in the pressure-sensitive adhesive layer in the intermediate state at the time of completing the initial drying is 50,000 cps or more and the thickness of the bottom of the recess is 5 μm or less.

The drying subsequent to the initial drying is preferably performed by blowing hot air having a temperature of 100 ° C. or more and a wind speed of 10 m / sec or more for about 30 seconds in order to shorten the time until the drying step is completed.

Further, in the above, as the release sheet, any material can be used as long as it has a function of releasing the pressure-sensitive adhesive, but as a typical one, it is preferable to use a so-called release paper treated with silicone. Examples of other peelable sheets include steel belts and rotating drums.

As the adhesive, a rubber-based adhesive, a synthetic resin-based adhesive or the like is used. As the rubber-based pressure-sensitive adhesive, for example, natural rubber or synthetic rubber, tackifying resin such as rosin-based, terpene-based, petroleum-based, or a softening agent such as various oils dissolved in a solvent such as n-hexane is preferable. Used for. Also,
As the synthetic resin adhesive, for example, acrylic acid ester such as butyl acrylate, 2-ethylhexyl acrylate and isononyl acrylate is used as a main monomer, and acrylic acid, acrylamide and N-vinyl-2-pyrrolidone are used as polar monomers. An acrylic pressure-sensitive adhesive obtained by copolymerizing a monomer and other monomers such as acrylic acid ester, methacrylic acid ester, styrene and vinyl acetate is preferably used. Further, other polyvinyl ether-based adhesives, polyisobutyl-based adhesives and the like can also be used.

Then, the organic solvent solution of the adhesive in the above, these pressure-sensitive adhesive component organic solvent, such as ethyl acetate, toluene, cyclohexane, n- hexane, there is dissolved in the alkane mixture such as the C ₅ -C ₇ All of them are already used in known cellophane tapes, craft tapes and the like. The viscosity of the organic solvent solution is preferably in the range of 500 to 6000 cps.

As a method for applying the organic solvent solution of the pressure-sensitive adhesive to the peelable sheet, various known methods such as a roll coater method, a knife coater method and an extrusion lip method are adopted.
The thickness of the applied pressure-sensitive adhesive solution layer is preferably in the range of 100 to 200 μm.

The size of water droplets to be sprayed is preferably 300 μm or less in maximum before adhering to the surface of the pressure-sensitive adhesive solution layer, and is preferably maximum particle size in the state after adhering to the surface of the adhesive solution layer. It is preferably in the range of 10 to 1000 μm.

Examples of the air-permeable base material include woven cloth, non-woven cloth, paper, cloth, open-cell foam sheet, or non-air-permeable base material, for example, synthetic resin sheet having many fine holes formed therein.

[Operation] In the present invention, since the hot air having a temperature of 60 ° C. or higher and a wind speed of 10 m / sec or less is sprayed on the surface of the pressure-sensitive adhesive solution layer for 10 seconds or more at the initial stage of drying the pressure-sensitive adhesive solution layer having water droplets sprinkled on the surface, It is possible to prevent the water droplets from completely evaporating before the viscosity of the pressure-sensitive adhesive solution layer increases due to the evaporation of the solvent and the pressure-sensitive adhesive solution layer stops flowing. Therefore, after the completion of the drying, it is possible to surely form the fine pores in the portion of the dried pressure-sensitive adhesive layer where the water droplets exist.

[Examples] Next, examples of the present invention and some comparative examples to be compared with the examples are given, and the evaluation test results of the respective air-permeable pressure-sensitive adhesive tapes produced are shown.

Example 1 A toluene solution of an acrylic pressure-sensitive adhesive (solid content 40% by weight, viscosity: 5000 cps) was applied on a release paper at a rate of 150 g / m ² to form a pressure-sensitive adhesive solution layer, and then the pressure-sensitive adhesive solution layer was not dried. While in the state, the particle diameter is 25-50 μm on the surface with a spray gun.
Of water was sprayed at 130 g / m ² .

Then, hot air having a temperature of 100 ° C. and a wind speed of 2 m / sec was blown onto the surface of the pressure-sensitive adhesive solution layer for 30 seconds to perform initial drying. afterwards,
Subsequently, hot air having a temperature of 140 ° C. and a wind speed of 20 m / sec was blown for 60 seconds to complete the drying, and a dry adhesive layer was obtained. The dried pressure-sensitive adhesive layer thus obtained was transferred to a breathable substrate (Tetron nonwoven fabric; manufactured by DuPont) to produce a breathable pressure-sensitive adhesive tape.

Example 2 A breathable pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the temperature of hot air in the initial drying conditions was 120 ° C and the blowing time was 60 seconds.

Comparative Example 1 A breathable pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the temperature of hot air under the initial drying conditions was 50 ° C.

Comparative Example 2 A breathable pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the hot air velocity under the initial drying conditions was 15 m / sec.

Comparative Example 3 A breathable pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the blowing time of hot air under the initial drying conditions was 5 seconds.

[Evaluation Test] The air-permeable pressure-sensitive adhesive tapes produced in Examples 1 to 2 and Comparative Examples 1 to 3 were tested for air permeability. The breathability test is based on JIS P8117 and is based on the Denso meter air permeability (300
cc air passed through a 6.45 cm ² hole). The results are shown in Table 1 together with the initial drying conditions.

[Effect of the Invention] According to the method of the present invention, fine pores can be reliably formed in the dried pressure-sensitive adhesive layer as described above. Therefore, it becomes possible to manufacture a breathable pressure-sensitive adhesive tape or sheet which has excellent breathability and has no variation in breathability.

[Brief description of drawings]

The drawings show the principle of forming a dry pressure-sensitive adhesive layer having fine holes on a peelable sheet by the method of the present invention. FIG. 1 is a schematic explanatory view, and FIG. 2 is a pressure-sensitive adhesive solution layer in each process. It is a figure which shows the change of an adhesive layer in order. (1) ... Releasable sheet, (2) ... Adhesive solution layer,
(2B) ... Dry adhesive layer.

Claims (1)

[Claims] 1. An organic solvent solution of a pressure-sensitive adhesive is applied to the surface of a release sheet to form a pressure-sensitive adhesive solution layer, and the surface of the pressure-sensitive adhesive solution layer is applied to the surface of the pressure-sensitive adhesive solution layer while the pressure-sensitive adhesive solution layer is in an undried state. In the method for producing a breathable pressure-sensitive adhesive tape or sheet by laminating a dried pressure-sensitive adhesive layer on a breathable substrate, which is then dried after spraying water droplets, at a temperature of 60 at the initial stage of the drying. A method for producing a breathable pressure-sensitive adhesive tape or sheet, which comprises blowing hot air having a temperature of ℃ or more and a velocity of 10 m / sec or less onto the surface of the pressure-sensitive adhesive solution layer for 10 seconds or more.