JP2000026814A - Kraft pressure-sensitive adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide kraft pressure-sensitive tapes which give an unwinding force suitable in the mechanical application as a winding and hardly cause crumbling of the load even when they are used in packing. SOLUTION: In the kraft pressure-sensitive adhesive sheet comprising a kraft paper having a pressure-sensitive adhesive layer on one side and a coating of a silicone resin on the reverse side which is formed as a winding, the silicone resin has been crosslinked by radiation and the unfolding power is 1-4 N/50 mm in rewinding by the method provided in JIS Z0237-10 (high speed rewinding), and the static coefficient of friction of the reverse sides with one another is not less than 0.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kraft pressure-sensitive adhesive tape used for packing and the like, and to a kraft pressure-sensitive adhesive tape which is unlikely to collapse even when a cardboard box or the like packed by using the tape is stacked.

[0002]

2. Description of the Related Art An ordinary adhesive tape, such as a kraft adhesive tape, maintains a shape as a wound body, imparts releasability to the adhesive layer, and controls a rewinding force. Coating of a release agent on the opposite side is performed. In the case of a kraft adhesive tape, silicone resin is widely used as a release agent in terms of release performance and cost. However, while silicone resin has good mold release properties, when adhesive tape using this as a mold release agent is used for packing cardboard boxes and the like, the friction between the backs of the adhesive tapes is small, so the boxes slip easily and the load easily collapses. Become.

As described above, when a silicone resin is used as a release agent, it is difficult to simultaneously satisfy the releasability and the non-slip property (referred to as non-slip property). It is possible to obtain non-slip properties by using other organic release agents, but it is not preferable because the release agents themselves are weak to heat and the cost is relatively high.

[0004] On the other hand, from the viewpoint of production, there is a problem that the cured film of the silicone resin changes with time. In general, in order to obtain a silicone resin used as a backing agent for an adhesive tape such as a kraft adhesive tape, a method in which an organopolysiloxane and an organohydrogenpolysiloxane are subjected to an addition reaction in the presence of a platinum-based catalyst is used. In such a composition, the curing reaction proceeds with time even after the cured film is formed, and the performance as an adhesive tape is changed by so-called after-cure. For this reason, it is difficult to apply the pressure-sensitive adhesive immediately after the curing, and the pressure-sensitive adhesive can be applied after a lapse of a certain time until the curing reaction is completed. This results in the retention of semi-finished products and is not efficient in production. Therefore, it is required that the reaction does not continue after curing and is completed within a few seconds.

To solve the above problem, Japanese Patent Application Laid-Open No.
There is a silicone composition for release described in JP-A-2-241964. However, in view of the reactivity of the composition, it does not reach the level where the pressure-sensitive adhesive can be applied immediately after the application.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a wrapping adhesive tape which provides a rewinding force suitable for mechanical application as a wound body and which does not easily collapse when used for packing. The purpose is to provide.

[0007]

The kraft pressure-sensitive adhesive tape of the present invention comprises a kraft paper having a pressure-sensitive adhesive layer provided on one surface thereof, a silicone resin coated on the back surface, and a wound kraft pressure-sensitive adhesive tape. It is cross-linked by radiation, has a deployment force of 1 to 4 N / 50 mm when unwound by a method specified in JIS Z0237 10 (high-speed unwinding force), and has a static friction coefficient of 0.2 or more between back surfaces. It is characterized by being.

The base material of the kraft pressure-sensitive adhesive tape is generally formed by clupak processing and has a high strength.
In general the 0 g / m ² are used those 72~75g / m ^2. In order to increase the coating accuracy of the silicone resin as a release agent and reduce the amount of coating, a polyolefin resin is often laminated.

Radiation-crosslinkable silicones are broadly classified into ultraviolet-curable and electron-beam-curable silicones, and the curing methods include radical addition, radical polymerization, cationic polymerization, and hydrosilylation reaction types. The radiation-curing type has a high reaction (curing) rate, completes curing in a few seconds, and has no factor to start the reaction thereafter. In the present invention, an electron beam-curable silicone is used in the present invention in that the ultraviolet ray-curing type is expensive because an ultraviolet absorber as a reaction initiator is expensive. Preferably, it is used.

[0010] The non-slip property after the adhesive tape is applied for packing also depends on the size of the box in which the adhesive tape is used and the weight of the contents. Is often the cause. Although there are several methods for evaluating the slipperiness, a static friction coefficient is generally used. From the test assuming the actual collapse of the load and the result of measuring the static friction coefficient on the back surface of the adhesive tape which is hard to collapse, it was found that the collapse of the load was hard to occur when the static friction coefficient was 0.2 or more. If this value is less than 0.2, the non-slip property is not sufficient. The coefficient of static friction of the back surface using a conventional silicone resin is 0.1 or less.

[0011] The non-slip property depends on the composition of the silicone resin, particularly the functional group to be reacted. For example, in the case of a radical polymerization type, an acrylic group is introduced into a siloxane chain, but the non-slip property changes depending on the content and the degree of polymerization.

On the other hand, if the releasability of the back surface of the adhesive tape, that is, the force for rewinding the wound adhesive tape is too large, the workability deteriorates. In particular, in recent years, there has been a tendency of mechanical sticking, and if the rewinding force is too large, the mechanical suitability may deteriorate. On the other hand, if the rewinding force is too small, the resistance at the time of rewinding is small, and the adhesive tape is fed out more than necessary, which hinders the process.

The optimum unwinding force is JIS Z 0237.
When deployed at 30 m / min specified in 10 “High-speed unwinding force”, it is necessary to be 4 N / 50 mm or less. Preferably, it is 3 N / 50 mm or less and 1 N / 50 mm or more.

The coating amount of the silicone resin is more economical as the coating amount is lower, but there is also a connection with the coating accuracy.
0.1 to 1 g / m ² is preferable, and more preferably 0.4 to 1 g / m ^2.
０．６0.6 g / m ² . Although the coating amount can be further reduced by diluting with a solvent, the cost required for drying the solvent and taking environmental measures is unavoidable.

(Function) The kraft pressure-sensitive adhesive tape of the present invention
Since the silicone resin as the backing agent is cross-linked by radiation, the cross-linking is completed quickly, there is no change with time of the film after curing, and the pressure-sensitive adhesive can be applied immediately after curing to produce the film. The unwinding force is 1 to 4
N / 50 mm, and the coefficient of static friction between the back surfaces is 0.2 or more, so that it is excellent in mechanical suitability for sticking, and it is unlikely that collapse of the load occurs even if the packages packed using this are stacked.

[0016]

Embodiments of the present invention will be described below. Example 1 Unbleached kraft paper subjected to clupak processing was laminated with polyethylene in an amount of 15 g / m ² .
A silicone release agent having a radical polymerization type acrylic group introduced on the laminate surface (trade name “X-62” manufactured by Shin-Etsu Chemical Co., Ltd.)
-7205 ”) as a solid content of 0.5 g / m ² , and then cured by irradiation with an electron beam of 165 kV · 3 Mrad. Immediately thereafter, a hot-melt pressure-sensitive adhesive containing SIS as a main component was applied to the other surface of the kraft paper at 50 g / m2.
The kraft pressure-sensitive adhesive tape immediately after curing was obtained by coating in the amount of ² and winding. Further, the above-mentioned pressure-sensitive adhesive tape was passed at 25 ° C. for 48 hours to obtain a kraft pressure-sensitive adhesive tape after 48 hours.

(Comparative Example 1) A release agent having a small acrylic group content (trade name "X-62-7" manufactured by Shin-Etsu Chemical Co., Ltd.)
989 "), a kraft pressure-sensitive adhesive tape immediately after curing and a kraft pressure-sensitive adhesive tape after 48 hours had been produced in the same manner as in Example 1.

Comparative Example 2 An organic release agent containing a long-chain alkyl group in a molecule was applied as a release agent in a solvent system.
Place in a 20 ° C. oven for 15 seconds and dry.
A kraft pressure-sensitive adhesive tape immediately after curing and after 48 hours was obtained in the same manner as in Example 1 except that a release layer of g / m ² was formed.

(Comparative Example 3) A heat-curable silicone was used as a release agent, and was applied at a coating amount of 1 g / m ^2.
A kraft pressure-sensitive adhesive tape immediately after curing and after 48 hours was obtained in the same manner as in Example 1 except that the coating was cured after heating at 0 ° C. for 30 seconds. However, the silicone tape migrated to the adhesive surface of the adhesive tape wound immediately after curing, and the ball tack value dropped by 4 points, indicating that the adhesive tape could not be used practically as an adhesive tape.

Performance evaluation (1) Rewinding force An adhesive tape having a width of 50 mm was used according to JIS Z 0237-10.
The resistance value at the time of rewinding at 30 m / min specified in the “high-speed rewinding force” was measured. (2) Coefficient of static friction The silicone-coated surface was set to a size of 35 × 70 mm and 20
The sample was attached to a 0 g weight, placed on the same silicone-coated surface, and the coefficient of static friction was measured. (3) Heat resistance test The adhesive tape was left in an oven at 60 ° C for 3 days, and then left at 25 ° C for 1 day. (4) Curability The silicone film before applying the pressure-sensitive adhesive was strongly rubbed with a finger five times, and clouding or falling was not observed. Table 1 shows the above results.

[0021]

[Table 1]

[0022]

According to the kraft adhesive tape of the present invention,
Since the silicone resin as the backing agent is cross-linked by radiation, the cross-linking is completed quickly, there is no change with time of the film after curing, and the adhesive can be applied immediately after curing. it can. In addition, since both the unwinding force from the adhesive tape and the non-slip property between the back surfaces are satisfied at the same time, the unwinding is easy during use and the machine is excellent in machine suitability. Further, even if cardboard boxes or the like packed by using the above are stacked, the collapse of the load hardly occurs.

Claims (1)

[Claims] 1. A kraft paper having a pressure-sensitive adhesive layer provided on one side, a silicone resin coated on the back side, and a rolled kraft pressure-sensitive adhesive tape, wherein the silicone resin is cross-linked by radiation.
A kraft adhesive tape characterized in that the unwinding force at the time of rewinding by the method specified in No. 0237 (high-speed unwinding force) is 1 to 4 N / 50 mm and the coefficient of static friction between the back surfaces is 0.2 or more. .