JP2014065810A - Manufacturing method of bubble-enclosed adhesive tape or sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a bubble-enclosed adhesive tape or sheet capable of realizing large bubble diameters regardless of types of substrates and enabling the verification of a homogeneously foamed state even when magnified by 100 times.SOLUTION: The provided manufacturing method of a bubble-enclosed adhesive tape or sheet is a method for manufacturing a bubble-enclosed adhesive tape or sheet wherein a bubble-enclosed tackifier layer is formed on at least one side of a substrate and comprises a melting step of heating and melting a tackifier raw ingredient including a thermoplastic resin till the melt viscosity thereof reaches 5000-200000 mPa s, a mixing step of adding 25-80 parts.vol. of a component gaseous at normal temperature and normal pressure to 100 parts.vol. of the tackifier raw ingredient melted and mixing within an environment wherein the liquid pressure is maintained at 3-10 MPa, and a pressure release step of forming, upon the completion of the mixing step, bubbles within the tackifier layer by releasing the pressure impressed onto the tackifier raw ingredient.

Description

  The present invention relates to a foamed adhesive tape and a method for producing a sheet.

  Conventionally, in the production of pressure-sensitive adhesive tapes and sheets, the pressure-sensitive adhesive layer contains fine closed cells to improve the pressure-sensitive adhesive properties (particularly the initial pressure-sensitive adhesive force and the adhesiveness to the rough surface). There has been proposed a method for realizing cost reduction by reducing the amount of use.

Here, Patent Documents 1 and 2 propose a method in which a heat decomposable foaming agent is contained in an adhesive layer and this is heated and foamed. Patent Document 3 proposes a method in which a vaporizable substance (for example, water) is contained in a base material and gasified to form closed cells in the pressure-sensitive adhesive layer. Further, Patent Documents 4 and 5 describe a method in which a gas is mixed in a hot-melt thermoplastic adhesive, the mixture is pressurized, then the pressure is released, and bubbles are formed in the adhesive. A method in which a pressure-sensitive adhesive sheet formed on at least one surface thereof is placed in a gas atmosphere at a pressure of 5 to 200 kg / cm ² , the atmospheric gas is dissolved in the pressure-sensitive adhesive layer under pressure, and then the pressure is released. Have been proposed.

JP-A-62-263278 Japanese Patent Publication No. 64-6678 Japanese Patent Publication No. 2-27705 JP-A-53-17645 Japanese Patent Laid-Open No. 08-199125

  Here, according to the methods of Patent Documents 1 and 2, there is a problem that the diameter of the obtained bubbles (hereinafter referred to as the bubble diameter) is small, and a sufficient expansion ratio cannot be obtained. Further, according to the technique of Patent Document 3, there is a problem that, although the bubble diameter obtained is large, the type of the substrate is limited to those capable of containing a vaporizable substance such as a nonwoven fabric. For example, regarding a plastic film, since water cannot be contained, steam foaming is impossible in the first place. In addition, with regard to the woven fabric, water can be absorbed into the portion of the yarn woven in the vertical and horizontal directions, so that water vapor foaming is possible, but conversely, there is a drawback that bubbles are generated only in the portion of the yarn. In addition, since bubbles tend to be unevenly distributed in the surface layer portion of one pressure-sensitive adhesive, it is difficult to uniformly foam the entire pressure-sensitive adhesive, and the tendency becomes more remarkable as the pressure-sensitive adhesive thickness increases. Furthermore, according to the methods of Patent Documents 4 and 5, there is a drawback that it is necessary to pressurize and release the pressure in the pressure chamber, which is a batch type and not a continuous type. In particular, Patent Document 4 has a drawback that the pressure is small and the pressure-sensitive adhesive cannot be foamed satisfactorily. Further, according to the method of Patent Document 5, bubbles are concentrated on the surface layer portion of the pressure-sensitive adhesive, and there is a drawback that a problem that bubbles are hardly generated inside the pressure-sensitive adhesive is likely to occur. Therefore, the present invention can realize a large bubble diameter and a high expansion ratio regardless of the type of base material, and can be confirmed to be uniformly foamed inside the pressure-sensitive adhesive even when enlarged to 100 times. It aims at providing the manufacturing method (especially manufacturing method which can be continuously produced) of an adhesive tape or a sheet | seat.

The present invention
In the method for producing a foamed pressure-sensitive adhesive sheet or tape in which a foamed pressure-sensitive adhesive layer is formed on at least one of the substrates,
A melting step in which a pressure-sensitive adhesive material containing a thermoplastic resin is heated and melted until the melt viscosity becomes 5000 to 200000 mPa · s;
In an environment where the liquid pressure is maintained at 3 to 10 MPa, a mixing step of adding and kneading 25 to 80 parts by volume of a gaseous component at normal temperature and normal pressure with respect to 100 parts by volume of the pressure-sensitive adhesive raw material,
After the mixing step, the pressure applied to the pressure-sensitive adhesive raw material is released, and a pressure release step of forming bubbles in the pressure-sensitive adhesive layer is included.

  Here, the pressure-sensitive adhesive material may include a styrene-based elastomer and a tackifier resin (that is, the bubble-containing pressure-sensitive adhesive sheet or tape may be a styrene-based hot-melt pressure-sensitive adhesive sheet or tape). The substrate may be made of a plastic film, a woven fabric, and a non-woven fabric. Further, the melt viscosity may be 10,000 to 100,000 mPa · s.

  According to the present invention, a large bubble diameter and a high expansion ratio can be realized regardless of the type of the substrate, and the bubbles are uniformly dispersed in the pressure-sensitive adhesive. There exists an effect that a manufacturing method can be provided.

FIG. 1 shows an extruder according to this embodiment. FIG. 2 is a photograph in which the surface of the hot-melt adhesive tape with bubble according to Example 7 is magnified 100 times. FIG. 3 is a photograph in which the surface of a hot-melt pressure-sensitive adhesive tape containing bubbles in the case of water foaming (cloth base material) is magnified 100 times. FIG. 4 is a photograph in which the surface of a hot-melt pressure-sensitive adhesive tape containing bubbles in the case of foaming with a pyrolytic chemical foaming agent (cloth base material) is magnified 100 times. FIG. 5 is a photograph in which the surface of the hot-melt adhesive tape with bubble according to Example 9 is magnified 100 times. FIG. 6 is a photograph in which the surface of the hot-melt adhesive tape with bubble according to Example 10 is magnified 100 times. FIG. 7 is a photograph in which the surface of the hot melt adhesive tape with bubbles according to Comparative Example 1 is magnified 100 times. FIG. 8 is a photograph in which the surface of the hot melt adhesive tape with bubbles according to Comparative Example 2 is magnified 100 times.

  Hereinafter, an embodiment of a method for producing a foamed pressure-sensitive adhesive tape or sheet according to the present invention (an embodiment of a method for producing a hot-melt adhesive) will be described. In addition, this invention is not limited to the said form, It can apply also to a solvent type adhesive and an emulsion type adhesive.

The method for producing a bubble-containing hot melt pressure-sensitive adhesive tape or sheet according to this embodiment is as follows:
A melting step in which a pressure-sensitive adhesive material containing a thermoplastic resin is heated and melted until the melt viscosity becomes 5000 to 200000 mPa · s;
In an environment where the liquid pressure is maintained at 3 to 10 MPa, a mixing step of adding and kneading 25 to 80 parts by volume of a gaseous component at normal temperature and normal pressure with respect to 100 parts by volume of the pressure-sensitive adhesive raw material,
After the mixing step, a pressure releasing step for releasing the pressure applied to the adhesive raw material,
A laminating step in which the pressure-sensitive adhesive material or the bubble-containing pressure-sensitive adhesive is applied to at least one of the substrates. Hereinafter, the manufacturing method will be described in detail.

<< 1. Raw material >>
<1-1. Adhesive raw material>
The pressure-sensitive adhesive raw material used in the production method according to this embodiment contains a thermoplastic resin as a main component. Furthermore, you may contain another component as needed. Hereinafter, each component and composition will be described in detail.

(1-1-1. Thermoplastic resin)
The thermoplastic resin that can be used in this embodiment is not particularly limited. For example, styrene-isoprene-styrene block copolymer (SIS), styrene-butylene-styrene block copolymer (SBS), styrene-ethylene / butylene- Styrenic elastomers such as styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-isoprene / propylene-styrene (SIPS); polyethylene, particularly ultra-low density polyethylene and polypropylene, Examples include olefin polymers such as ethylene / vinyl acetate copolymers; acrylic polymers containing alkyl esters such as acrylic acid and methacrylic acid as components; polyester systems; polyamide systems; urethane systems; These may be used alone or in combination of two or more. Among these, it is preferable to use a styrene-based elastomer from the viewpoints of adhesive properties and practicality.

(1-1-2. Other components)
Examples of other components include tackifier resins, softeners, fillers, pigments, anti-aging agents, stabilizers, and the like. First, examples of the tackifier resin include aliphatic petroleum resins, coumarone-indene resins, alicyclic petroleum resins, terpene resins, terpene phenol resins, and rosin resins. These may be used alone or in combination of two or more. Examples of the softening agent include various oils such as paraffins, polybutenes, polyisobutylenes and terpenes, or hydrogenated products or partially hydrogenated products thereof. These may be used alone or in combination of two or more. Furthermore, examples of the filler include metal oxides such as titanium oxide and iron oxide, talc, calcium carbonate, clay, and carbon black. These may be used alone or in combination of two or more.

(1-1-3. Compounding amount)
First, a thermoplastic resin contains 17-67 mass% on the basis of the total mass of the adhesive raw material which concerns on this form, for example. Moreover, tackifying resin contains 9-73 mass%, for example on the basis of the total mass of the adhesive raw material which concerns on this form. Furthermore, a softener contains 2-61 mass% on the basis of the total mass of the adhesive raw material which concerns on this form, for example. However, the amount is merely an embodiment of the present invention as described above, and is not limited to the range.

<1-2. Ingredients that are gaseous at normal temperature and pressure>
The component that is a gas at normal temperature and normal pressure according to the present embodiment is not particularly limited as long as it is a gas that can be dissolved in the pressure-sensitive adhesive material. For example, inorganic gases such as nitrogen, air, and carbon dioxide, helium, argon, and the like Noble gases and organic gases such as propane, butane and chlorofluorocarbon. Here, the normal temperature and normal pressure mean a temperature of 23 ° C. and an absolute pressure of 101325 Pa.

<1-3. Base material>
The base material according to the present embodiment is not particularly limited. For example, a synthetic resin film made of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, soft polyvinyl chloride, polyurethane, polyester represented by polyethylene terephthalate (PET), or the like. And non-woven fabric, woven fabric, high-quality paper, craft paper, glassine paper, coated paper, cast coated paper, resin-impregnated paper, metal foil laminate film, metal vapor-deposited film and the like. One or more of these may be laminated or laminated. In addition, since the applied adhesive is high temperature, it is necessary to pay attention to the softening point of the substrate.

≪2. Process >>
<2-1. Device configuration>
An extruder that can be used in this embodiment will be described with reference to FIG. In addition, the said extruder is an example to the last, and does not limit this invention. The extruder A includes an adhesive raw material tank 1-1 in which a molten adhesive raw material is stocked, a gas tank 1-2 in which liquefied gas (for example, liquefied nitrogen) is stocked, and an adhesive raw material tank 1- 1, a first pump 2-1 for sending a molten adhesive material in the downstream, a twin screw 3 for mixing the adhesive material and gas at a predetermined ratio, and a mixture (gas and adhesive) A second pump 2-2 for quantitatively sending the mixture with the raw material) downstream, a head 5 for discharging the mixture, and a line 6 for passing each fluid. The pressure is maintained up to the tip of the coating head (however, pressure loss due to distance is excluded).

<2-2. Melting process>
In the melting step according to this embodiment, the pressure-sensitive adhesive material containing a thermoplastic resin is heated until the melt viscosity becomes 5000 to 200000 mPa · s, preferably 5000 to 150,000 mPa · s, and more preferably 10000 to 100000 mPa · s. Melt. In addition, the melt viscosity prescribed | regulated here is a viscosity of the adhesive raw material just before mixing with gas with the twin screw 3. FIG. If the melt viscosity is low, the foam diameter tends to increase when the foam is expanded, and the expansion ratio tends to increase. If the melt viscosity is high, the foam diameter tends to decrease because the foam diameter becomes small when foamed. is there. In particular, when the viscosity exceeds 200,000 mPa · s, the expansion ratio is remarkably lowered. On the other hand, when the viscosity is less than 5000 mPa · s, the gas contained in the melted pressure-sensitive adhesive tends to escape, which is not preferable. Here, in the case of a styrene-based hot-melt pressure-sensitive adhesive, a suitable temperature for realizing the viscosity is 140 to 230 ° C, and more preferably 150 to 230 ° C. Here, “melt viscosity” in the present specification is the viscosity of the adhesive completely melted in the melter (1-1 in FIG. 1) at the kneading temperature (temperature 1-1 in FIG. 1). And a viscometer (Viscotester VT-03F or Viscotester VT-04F, manufactured by Rion Co., Ltd.).

<2-3. Mixing process>
The mixing step according to the present embodiment includes a twin screw 3 in an environment in which the pressure (hydraulic pressure) of the system (in the path of 2-1 and 2-2) is maintained at 3 to 10 MPa (preferably 5 to 7 MPa). Rotation of the pressure sensitive adhesive raw material and the component that is gaseous at normal temperature and normal pressure with respect to 100 parts by volume of the molten pressure sensitive adhesive raw material, 25 to 80 parts by volume (preferably 30 parts by volume) of the gaseous component at normal temperature and normal pressure To 50 parts by volume) and mixing. In addition, adjustment of the mixing ratio between the pressure-sensitive adhesive raw material and a component that is a gas at normal temperature and normal pressure can be appropriately performed by changing the rotation ratio of the twin screw 3. Here, in the case of a styrene-based hot melt adhesive, a suitable temperature in the mixing step is 140 to 230 ° C. On the other hand, if the hydraulic pressure is less than 3 MPa, the differential pressure between the pressure in the system of the apparatus and the atmospheric pressure is small, bubbles having a large bubble diameter cannot be obtained, and the expansion ratio is lowered, which is not preferable. On the other hand, if the pressure exceeds 10 MPa, the load on the apparatus is large, so that continuous coating for a long time becomes difficult and the worst apparatus may be damaged. In particular, it is preferable to carry out at 7 MPa or less from the viewpoint of stable coating. When the component that is gaseous at normal temperature and normal pressure is less than 25 parts by volume with respect to 100 parts by volume of the melted adhesive raw material, the amount of gas is too small, and the expansion ratio decreases, and exceeds 80 parts by volume. In some cases, increasing the amount of gas further is inefficient because the change in expansion ratio is very small.

<2-4. Pressure release process>
The pressure release process according to this embodiment is a process of releasing the pressure applied to the gas mixed with the twin screw 3 (adhesive raw material + component at normal temperature and normal pressure). When the illustrated extruder is used, it is carried out by extruding the adhesive material in which the gas is dissolved through the second pump 2-2 and the head 5 from the twin screw 3 in a high temperature and high pressure state. In the pressure-sensitive adhesive raw material, the pressure applied to the substance that is a gas at normal temperature and normal pressure is reduced, so that when the pressure is released, foaming occurs inside the pressure-sensitive adhesive and fine bubbles are formed.

<2-4. Lamination process>
The lamination process according to this embodiment is typically performed simultaneously with or immediately after the pressure release process. A typical example is an embodiment (typically surface coating) in which an adhesive composition in which a gas is melted is extruded onto a substrate from an extruder having a high temperature and high pressure inside through a head 5. it can. A coextrusion method in which the pressure-sensitive adhesive is made into two layers or the base material is melted and the pressure-sensitive adhesive and the base material are extruded and laminated at the same time may be employed. The coating pattern is not particularly limited, and examples thereof include slot coat, curtain coat, foam, bead, dot, porous coat, spray, spiral spray, thread rubber spray, and summit spray.

  Here, after lamination, it is preferable to cool the high-temperature pressure-sensitive adhesive layer with a cooling roll. By this cooling, it is possible to suppress excessive growth of the bubble diameter. Here, in the case of a styrene-based hot-melt pressure-sensitive adhesive, it is preferable to set the temperature of the cooling roll to 10 to 40 ° C.

≪3. Foamed adhesive tape or sheet >>
<3-1. Structure>
First, the thickness of an adhesive layer is not specifically limited, For example, it can select from the range of about 1-1000 micrometers (preferably 10-500 micrometers). In general, the thinner the adhesive, the easier it is for bubbles to escape and it is difficult to fire. Moreover, the thickness of a base material is not specifically limited, For example, it can select from the range of about 10-300 micrometers, Preferably about 30-200 micrometers. Moreover, the adhesive tape or sheet which concerns on this form may be formed in both surfaces, even if the adhesive layer is formed only in the one surface of a base material. The base material layer may be a laminate. Furthermore, layers (for example, a release liner, a primer layer, and other functional layers) other than the base material layer and the pressure-sensitive adhesive layer may exist.

<3-2. Properties (especially properties of the adhesive layer)>
The expansion ratio of the pressure-sensitive adhesive layer in the bubble-containing pressure-sensitive adhesive tape or sheet is preferably 20 to 50%, more preferably 25 to 50%. Thus, since the expansion ratio is high, it can be peeled cleanly without residue in a re-peelability test for SUS plate and proling. Here, the expansion ratio (bubble occupancy) in this specification is calculated by the following equation.

  Using the apparatus shown in FIG. 1, bubbled hot-melt pressure-sensitive adhesive tapes according to Examples and Comparative Examples were produced under the conditions shown in Table 1 (composition of pressure-sensitive adhesive raw material) and Table 2. Here, for any of the examples and comparative examples, a styrene-based thermoplastic resin composition (styrene-isoprene block copolymer) was used as the thermoplastic resin, and nitrogen was used as the gas. The kneading temperature is the melter temperature (melter temperature: the temperature of “1-1” in FIG. 1). The results are shown in Table 2. In Table 2, the “gas ratio” is the volume part (%) of the component that is a gas at normal temperature and normal pressure with respect to 100 parts by volume of the melted adhesive raw material. Moreover, FIG. 2 is a surface photograph of the hot-melt adhesive tape with bubbles according to Example 8, and FIG. 3 is a photograph of the surface of the hot-melt adhesive tape with bubbles in the case of water foaming (cloth base material). . As can be seen from these drawings, bubbles are uniformly distributed in the former, whereas the latter foams only around the smoky moss. Further, as can be seen from FIGS. 4 to 6, it can be seen that the hot-melt pressure-sensitive adhesive tape according to the example has a larger cell diameter as compared with the case of foaming with a pyrolytic chemical foaming agent.

Industrial applicability

According to the present invention, it is possible to produce a bubble-containing pressure-sensitive adhesive having a large cell diameter and a large expansion ratio. The pressure-sensitive adhesive produced using the present invention is expected to be excellent in various adhesive properties such as rough surface adhesion and low-temperature properties.

Claims (4)

In the method for producing a foamed pressure-sensitive adhesive sheet or tape in which a foamed pressure-sensitive adhesive layer is formed on at least one surface of the substrate,
A melting step in which a pressure-sensitive adhesive material containing a thermoplastic resin is heated and melted until the melt viscosity becomes 5000 to 200000 mPa · s;
In an environment where the liquid pressure is maintained at 3 to 10 MPa, a mixing step of adding and kneading 25 to 80 parts by volume of a gaseous component at normal temperature and normal pressure with respect to 100 parts by volume of the pressure-sensitive adhesive raw material,
A method for producing a bubble-containing pressure-sensitive adhesive, comprising a pressure release step of releasing a pressure applied to the pressure-sensitive adhesive material after the mixing step.   The manufacturing method of Claim 1 with which an adhesive raw material contains a styrene-type elastomer and tackifying resin.   The manufacturing method of Claim 1 or 2 whose base material is 1 type, or 2 or more types chosen from the group which consists of a plastic film, a woven fabric, and a nonwoven fabric.   The manufacturing method as described in any one of Claims 1-3 whose melt viscosity is the range of 10,000-100,000 mPa * s.