JPH0143388Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an adhesive tape that has improved adhesive strength between a base sheet and an adhesive layer and is used for corrosion protection of steel pipes, electrical insulation, etc. Usually, as a tape for corrosion protection of steel pipes or for electrical insulation, a tape is used in which a rubber adhesive composition is bonded to a base sheet mainly made of polyolefin resin.

Such adhesive tapes are usually manufactured by the following method. First, a polyolefin resin such as polyethylene, ethylene-propylene copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, or a blend thereof is processed by inflation, T-die extrusion, or calendar processing. It is formed into a sheet body of a predetermined thickness by a method or the like.

On the other hand, rubber adhesives are based on butyl rubber, ethylene propylene rubber, natural rubber, etc., and add polyisobutylene, resin thickeners, etc. to give them tackiness, and if necessary fillers, processing aids, etc.
Anti-aging agents and the like are added, and these are made into a uniform mixture using a Banbury, kneader, or roll mill.

The base sheet and the adhesive are pasted together using a calendar or the like to form an adhesive sheet with an adhesive layer formed on one side of the base sheet. and must be sufficiently bonded in this bonding process. If the adhesion between the two is insufficient, the base sheet and the adhesive layer are likely to separate, and if such separation occurs, serious defects will occur when the tape is wrapped around a steel pipe or electrical conductor.

In order to improve the adhesiveness between the adhesive layer and the base sheet, the base sheet is heated in advance when bonding the two. A method such as activating the bonding surface of the base sheet by corona discharge or the like is applied. Alternatively, a resin that has better adhesion with the adhesive layer than the polymer for the base sheet may be added to the molded product of the base sheet by a method such as simultaneous two-layer extrusion to the extent that it does not significantly affect the properties of the base material. A method such as providing a thick layer is used.

On the other hand, recently, the range of applications for anti-corrosion adhesive tapes, adhesive tapes for electrical insulation, etc. has expanded, and the number of applications has increased to 100.
Increasingly, devices are used at high temperatures of ℃ or higher. Therefore, in order to withstand such harsh usage conditions, radiation irradiation, chemical crosslinking, and the like, which are known as methods for improving heat resistance, are generally applied when producing the base sheet.

However, due to such radiation irradiation treatment,
Even if heat treatment is performed using an infrared heater or the like just before bonding the adhesive to a base sheet that has introduced cross-linking and improved heat resistance using a calendar roll, the base sheet will not work. The surface of the material sheet does not soften easily, and therefore, it has been difficult to achieve sufficient adhesion between the adhesive layer and the base sheet.

Even if corona treatment was applied to the surface of the base sheet to compensate for such problems, the effect was weak.
In addition, for this reason, even if a thin layer of resin is provided on the surface of the base sheet during extrusion molding of the base sheet, which has higher adhesiveness to the adhesive layer than the base sheet material, the base sheet Because the thin layer is also crosslinked during the radiation treatment performed to improve the heat resistance of the adhesive layer, the effect of improving the adhesiveness with the pressure-sensitive adhesive layer is inhibited.

In addition, considering the application of a method in which a base sheet is made from a resin composition to which a chemical crosslinking agent such as peroxide is added, and this is heated and crosslinked, it is possible to apply a thin layer of highly adhesive resin onto the base sheet. The thin layer will not be crosslinked unless a crosslinking agent is added to the thin layer forming material, but the thin layer will melt during the heat treatment during crosslinking of the base sheet containing the crosslinking agent. However, this may cause deformation or adhesion of the base sheets, making manufacturing difficult. This invention was developed by focusing on the above-mentioned points, and was the result of intensive research to develop an adhesive tape that has excellent heat resistance properties and has strong adhesion between the base sheet and the rubber adhesive layer. We were able to develop an adhesive tape. That is, as shown in the drawings, the adhesive tape of the present invention has a silane-crosslinked polyolefin polymer layer 2 on one side and a non-crosslinked polyolefin polymer layer 2 on a base sheet 4 having a silane crosslinked polyolefin polymer layer 2 on the other side.
It is characterized in that a rubber adhesive layer 3 is formed on the surface.

Hereinafter, a typical manufacturing method of the adhesive tape of the present invention will be explained step by step.

The silane-crosslinked polyolefin-based polymer sheet is produced by adding, for example, polyethylene, ethylene-propylene copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate resin, etc. singly or in a mixture of two or more, for example, vinyltrimethoxysilane, etc. Adding an organic silane compound and a free radical generator such as an organic peroxide,
These are reacted to produce a silane-grafted polyolefin polymer, and a predetermined amount of silanol condensation catalyst is added to this silane-grafted polyolefin polymer. Using this mixture, a conventional inflation method, T-die method, etc. It is made by extrusion molding the sheet body. A thin film of a non-crosslinked polyolefin resin, which is the same as or different from the silane-grafted polyolefin polymer, is formed on the silane-grafted polyolefin polymer sheet. In addition to a method of manufacturing by coextruding a thin film of a non-crosslinked polyolefin polymer, there is a method of pressure laminating a thin film of the non-crosslinked polyolefin polymer onto a silane-grafted polyolefin polymer sheet.

The thin film of the non-crosslinked polyolefin polymer on the composite sheet thus produced is neither silane grafted nor contains a silanol condensation catalyst. The thus prepared composite sheet is exposed to a moisture atmosphere to cause a crosslinking reaction, thereby forming a base sheet.

While heating the base sheet thus obtained,
The material is supplied to a calender roll, and a rubber adhesive is bonded to the thin layer side of the non-crosslinked polyolefin polymer. If the thin film surface of the non-crosslinked polyolefin resin of the base sheet is subjected to corona treatment prior to lamination of the adhesive, the adhesiveness with the rubber adhesive layer can be further increased.

In the adhesive tape of the present invention obtained as described above, the polyolefin resin that is the main component of the base sheet is cross-linked with silane, so it does not soften at the melting point of ordinary polyolefins, and therefore cannot be used at high temperatures. On the other hand, since the thin layer of non-crosslinked polyolefin polymer formed on one side of the silane-grafted polyolefin resin layer is not cross-linked at all, it is difficult to bond with the rubber adhesive layer provided on the layer. It is easily softened by heat treatment of the base sheet, which is sometimes carried out, and can be easily and sufficiently bonded to the rubber adhesive layer. Therefore, the adhesive tape of the present invention exhibits extremely excellent properties without any peeling between the polyolefin resin film and the rubber adhesive layer.

Next, an embodiment of the present invention will be described. (All parts below refer to parts by weight.) Example A composition containing 2.0 parts of vinyl methoxysilane and 0.18 parts of dicumyl peroxide to 100 parts of polyethylene was extruded at a temperature of about 200°C. Knead with
Silane-grafted polyethylene in the form of pellets was obtained. Next, 5 parts of pellets of a mixture having the following composition were added to 95 parts of these pellets.

100 parts of polyethylene 1 part of dibutyltin dilaurylate 1 part of anti-aging agent
A composite sheet was created by feeding a die extruder and extruding a 0.03 mm thick non-crosslinked polyethylene thin layer onto a 0.30 mm thick silane-grafted polyethylene sheet, which was then immersed in 60℃ hot water. Cross-linked.

Next, the non-crosslinked polyethylene thin layer of the composite sheet thus created was subjected to a corona discharge treatment, and then, while heating this composite sheet with an infrared heater, a separately prepared layer was prepared on the polyethylene thin layer that had been subjected to the corona discharge treatment. An adhesive tape having the following composition was laminated to a thickness of 0.30 mm.

Adhesive composition Butyl rubber 100 parts Polyethylene 55 parts Polyisobutylene 85 parts Light oil 10 parts Anti-aging agent 1.5 parts Carbon black 0.5 parts For comparison, an adhesive of the same composition was placed on a base sheet made only of silane-grafted polyethylene.
Comparative adhesive tapes were made by laminating them to a thickness of 0.30 mm.

The adhesive tape of the present invention and the adhesive tape for comparison were kept in a constant temperature bath at 60°C for 3 months in a rolled state, and then at a low temperature of -30°C.
Although it was stored for several hours and rewound at the same temperature,
The product of the present invention could be rewound without any problems in any case, but the comparative product often experienced peeling between the adhesive layer and the base sheet.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of the adhesive tape of the present invention. DESCRIPTION OF SYMBOLS 1... Silang-grafted polyolefin resin layer, 2... Polyolefin resin thin layer, 3... Rubber adhesive layer, 4... Base material sheet.

Claims (1)

[Scope of utility model registration request] A heat-resistant adhesive characterized in that a rubber adhesive layer is formed on the surface of the non-crosslinked polyolefin polymer layer of a base sheet having a silane crosslinked polyolefin polymer layer on one side and a non-crosslinked polyolefin polymer layer on the other side. tape.