JP2000008297A - Production of release paper for kraft adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing release paper for a kraft adhesive tape obtained by using a silicone-based and non-solvent type releasing agent excellent in safety and pollution by which the quality and the productivity are not damaged by the attachment and the remaining of a paper powder generated from Clupak paper on a coating roller. SOLUTION: A silicone-based non-solvent type releasing agent comprising a polyorganosiloxane having 20-90 mPa (measured at 60 rpm by a B-type viscometer) at the normal temperature is applied on a base material for a kraft adhesive tape having a barrier layer by using a regularly rolling three roll offset gravure coater, and cross-linking the coated releasing agent.

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 a release paper for kraft pressure-sensitive adhesive tapes using a solventless release agent.

[0002]

2. Description of the Related Art A method of manufacturing a release paper for kraft adhesive tape is to apply silicone coating to the surface of kraft stretched paper (hereinafter referred to as "Clapak paper") in order to improve the peelability of the kraft adhesive tape wound in a cylindrical shape. For the purpose of maximizing the releasability by suppressing the penetration of the release agent such as liquid as much as possible, a base material or an aqueous resin on which a polyethylene laminate layer having a thickness of about 10 to 25 microns is formed by an extrusion processing method. A method is generally used in which a substrate having a dense barrier layer having a main component as a main component is coated with a solution in which a release agent or a release agent, that is, a silicone resin or the like is dissolved in an organic solvent such as toluene. It is.

[0003] Release agents for release paper for kraft adhesive tapes include silicone resins, fluororesins, aminoalkyd resins, polyester resins and the like, and are used as emulsion type, solvent type or solventless type. used. The silicone resin for release paper generally comprises a main polymer in which vinyl groups are introduced into dimethylpolyorganosiloxane, an organohydrogenpolysiloxane as a crosslinking agent, a platinum-based catalyst, and a reaction control agent. A cured film is formed by a crosslinking reaction. At present, the silicone is generally obtained by diluting a release agent with a solvent, that is, a so-called solvent-type silicone is applied to a release paper substrate. The reason is that when coating the release agent, the fluidity is appropriately adjusted by diluting with a solvent to form a uniform layer of the release agent film on the substrate surface,
The performance of the release agent can be easily maximized. However, in recent years, there has been a strong demand for consideration of safety and pollution, and there has been a strong demand for solvent-free release agents from the viewpoint of maintaining the health of workers.

[0004] On the other hand, the biggest problem in coating the solventless silicone onto clupak paper is that brown fibrous powder (hereinafter referred to as paper powder) falls off the clupak paper during the coating process.
As a result, a uniform coating layer is not adhered to the surface of the coating roll, and a uniform coating layer cannot be obtained. This causes a cause of peeling failure, and furthermore, the operation becomes difficult.

For this reason, in order to prevent the paper dust from falling off, the surface of the clupak paper is subjected to a secondary treatment for increasing the paper strength, or the coating speed when the silicone liquid is coated is extremely reduced. And so on, both of which result in a significant increase in cost and an extremely low productivity. In addition, in order to prevent paper dust from adhering to the coated surface, the process of applying a polyethylene laminate layer or a barrier layer mainly composed of an aqueous resin and the like and the process of applying a silicone liquid are regarded as one process. It is necessary to prevent the base material from being rolled in advance, but significant equipment remodeling is required.

[0006]

For the above reasons, there has been a strong demand for a release paper for kraft pressure-sensitive adhesive tapes using a solvent-free release agent which is excellent in safety and pollution. The production method of the release paper for kraft adhesive tape which can sufficiently satisfy the above conditions is not provided.

An object of the present invention is to provide a surface of clupak paper,
A base material or a polyethylene laminate layer having a thickness of about 10 to 25 microns formed by a melt extrusion processing method,
Regarding the production of release paper for kraft adhesive tape, which is a solvent-free silicone liquid coated as a release agent on a substrate having a dense structure barrier layer mainly composed of an aqueous resin, etc., from Clupak paper in the coating process with adhesive paper powder generated is to the coating roll, by remaining, it is to provide a production method excellent without impairing quality and productivity.

[0008]

In view of this situation, the present inventors have conducted extensive and extensive research on the properties of release agents, coating methods, coating conditions, and the like. In addition, by applying a specific coating method, paper dust is not generated from clupak paper in the coating process, so that the paper powder adheres to and remains on the coating roll surface and does not impair the quality or productivity. Thus, a production method having high productivity and quality was completed, and the present invention was achieved. The present invention relates to a release paper for a kraft pressure-sensitive adhesive tape coated with a release agent, wherein the release agent is 20 to 90 mPa (60 r.
A method for producing a release paper for a kraft pressure-sensitive adhesive tape, comprising coating a silicone-based solvent-free release agent comprising a polyorganosiloxane having a pmB type viscosity) with a forward three-roll offset gravure coater and crosslinking. is there.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a release paper for a kraft adhesive tape coated with a release agent, wherein the release agent is a polyorganosiloxane made of a polyorganosiloxane having a viscosity of 20 to 90 mPa (60 rpm B type viscosity) at room temperature. A method for producing a release paper for kraft adhesive tape, wherein a solvent-type release agent is coated with a forward three-roll offset gravure coater and crosslinked, and no paper powder is generated from clupak paper in the coating step. Therefore, it is possible to manufacture a release paper for a kraft adhesive tape having excellent productivity and quality without causing paper powder to adhere and remain on the coating roll surface and impairing quality and productivity.

The inventors of the present invention have repeatedly conducted a test on a laboratory scale and a confirmation test on an actual machine to determine the cause of the drop of paper powder from the clupak paper into the silicone liquid. A shear force acts on the coating roll, coating element (coater head), and the surface of the clupak paper through a high silicone liquid, and fine shrinkage wrinkles are applied for the purpose of enhancing elongation, and the surface has a rough structure. Has been found to be caused by the rubbing of the clupak paper, which is caused by rubbing, as a result of falling off and dispersing as brown fibrous powder, that is, paper powder, or adhering to the coated surface.

Further, the present inventors have conducted intensive studies to eliminate the above-mentioned causes, and as a result, shearing of the coating roll and the like, the coating element (coater head), and the surface of the clupak paper through the silicone liquid. The force is applied, and fine shrinking wrinkles are given for the purpose of enhancing elongation, and the clumpak paper with a rough surface is damaged by rubbing, brown fibrous powder,
In other words, in order to prevent the powder particles from falling off and dispersed,
By applying a silicone-based solvent-free release agent comprising a polyorganosiloxane having a release agent having a viscosity of 20 to 90 mPa (60 rpmB type viscosity) at room temperature with a forward three-roll offset gravure coater, the Clepack paper is used in the coating process. The paper discovered that paper powder could be dropped and dispersed in the coating liquid, adhered and remained on the coating roll surface, and release paper with excellent productivity and quality could be produced without impairing quality and productivity. The invention was completed.

The solvent-free silicone used in the present invention is a polyorganosiloxane derivative, which is generally called an addition silicone, which is cured by the action of a platinum catalyst under heating to exhibit releasability. There is no particular limitation on the chemical structure, concentration, etc. of the compound, and a cross-linking agent or the like usually blended for crosslinking and polymerizing the organosiloxane derivatives is arbitrarily selected and added in order to obtain a desired peeling force. The silicone liquid applied to the clupak paper is 20 to 90 mP at room temperature.
What is necessary is just to have the property which has a (60 rpmB type viscosity).

The silicone liquid applied to the clupak paper is applied in the range of 0.2 to 2.0 g / m ² (dry weight) in consideration of the release performance and the price of the expensive silicone liquid. Silicone liquid at room temperature 20mPa (60rpm)
(B-type viscosity) is less than, the forward rotation three roll offset gravure coater of the present invention does not lead to obtaining the desired coating amount, and if the gravure roll mesh is roughened to obtain the desired coating amount, A flat release agent layer cannot be obtained, resulting in remarkable reduction in release performance. On the other hand, the silicone liquid is 90 mPa (60 rpm) at room temperature.
When the viscosity exceeds (mB type viscosity), a shear force acts on the surface of the clupak paper, and fine shrinkage wrinkles are imparted for the purpose of enhancing elongation, and the clumpak paper having a rough surface is damaged by rubbing, and brown. As a result, the particles fall off and disperse as a fibrous powder, that is, paper powder, adhere to the surface of the coating roll, and remain, and the object of the present invention cannot be achieved.

The platinum-based catalyst used here plays a particularly important role in accelerating the addition reaction of the organosiloxane, but platinum platinum catalysts such as chloroplatinic acid and chloroplatinic acid are used. Acid, alcoholic compound of chloroplatinic acid,
Known compounds such as aldehyde compounds or complex salts of chloroplatinic acid and various olefins can be selected and used.

Further, at room temperature of the present invention, it is 20 to 90 mPa.
Silicone liquid having a viscosity of (60 rpmB type viscosity) is not commercially available as a silicone for a release agent at present because the present invention is based on the groundbreaking idea of the present inventors. It can be obtained by requesting production from certain Toray Dow Corning, Shin-Etsu Chemical and Arakawa Chemical Industries.

As a method for applying the solventless release agent according to the present invention, it is necessary to use a forward-rotating three-roll offset gravure coater. Generally, as equipment for applying a solvent-type silicone liquid, as described above, the coating amount is 0.2 to 2.
0 g / m ^2, and coating speed is 100 to 800
m / min, which is fast, so that these conditions can be met by selecting and using appropriate coaters such as Meyer bar coating, forward offset gravure coating, reverse offset gravure coating, and forward 5-roll coating. Is done.

However, in all of the other coaters except for the three-roll forward gravure coater, a shear force acts on the surface of the clupak paper, and fine shrinkage wrinkles are provided for the purpose of enhancing elongation, and the surface has a rough structure. Is not able to prevent brown paper powder from dropping and dispersing in the silicone liquid, adhering to the coating roll surface, and remaining, and the release agent is kept at room temperature.
It is a silicone-based solventless release agent having a viscosity of 0 to 90 mPa (60 rpm B type viscosity), and the object of the present invention can be achieved only by satisfying the requirement of applying the release agent by a forward three-roll offset gravure coater. is there.

The stretched kraft paper of the present invention, that is, Krupak paper, is a base paper mainly made of wood pulp specified by JIS P 3412-1976R, and is a Krupak for imparting fine shrinkage wrinkles for the purpose of enhancing extensibility. It is manufactured by a fourdrinier multi-cylinder paper machine equipped with a processing facility, and is a general term for unbleached clumped paper mainly containing unbleached pulp, bleached clumped paper, colored clumped paper, and the like.

The pressure-sensitive adhesive applied to the release paper for kraft pressure-sensitive adhesive tapes of the present invention may be any of natural rubber-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, and acrylic emulzine-based pressure-sensitive adhesives as required. Can be selected and used.

Further, the production method of the present invention is not limited to a so-called single-sided adhesive tape in which a release agent is coated on one side of a kraft stretched paper and subjected to adhesive processing, and a double-sided release paper is prepared by performing similar processing on both sides. It can be applied to a double-sided adhesive tape.

[0021]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples. In each example, "parts" indicates "parts by weight" unless otherwise specified.

Example 1 A substrate for a kraft pressure-sensitive adhesive tape was produced by the following steps. (1) Papermaking of base paper First, a stock having the following composition was prepared. Ingredients Weight-Softwood kraft pulp (degree of beating: 570 ml) 100 parts-30% reinforced rosin sizing agent (trademark: SPE manufactured by Arakawa Chemical Industries) 0.3 parts-30% aluminum sulfate 2 parts Next, from this stock, Clupak paper A base paper having a rice basis weight of 73 g / m ^{2 was} produced by a fourdrinier multi-cylinder paper machine equipped with processing equipment. The density of the base paper thus obtained is 0.84 g / m
^2, Oken type smoothness of the dryer cylinder contact surfaces of the base paper was 34 seconds. (2) Formation of barrier layer A low-density polyetherene (manufactured by Sumitomo Chemical Co., Ltd.) melted on the base paper was laminated by a laboratory melt extruder to prepare a substrate for a kraft adhesive tape. As a result of observing the cross section of the substrate for a kraft pressure-sensitive adhesive tape with a scanning electron microscope, the thickness of the polyethylene laminate layer was about 19 μm. (3) Coating of release agent A coating machine equipped with a three-roll forward offset gravure coater on the base material on which the barrier layer was formed was used.
A silicone-based solventless release agent (manufactured by Arakawa Chemical Industries) having a mPa (viscosity of 60 rpm B) was applied to obtain a release paper. The roll of the gravure coater used was 200 mesh,
The coating speed was 300 m / min. The silicone coating amount measured by X-ray fluorescence analysis was 0.45 g.
/ M ² . (4) Adhesive tape processing A self-made natural rubber-based adhesive is applied on the silicone-coated surface of the release paper using an applicator bar, and is superimposed on the back surface of the Krupak paper to create a bonded paper simulating a kraft adhesive tape. did. (5) Evaluation of coating property, coated surface condition and release performance Observation of the state of paper powder falling off and dispersed from clupak paper at the time of the release agent coating, evaluation of the formed silicone surface condition, and simulation of kraft adhesive tape The peelability of the laminated paper was evaluated (peeling by hand was evaluated for practicality). The results are shown in Table 1.

Example 2 In the same manner as in Example 1, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, instead of the low-density polyethylene for a barrier layer of Example 1, a coating solution for a barrier layer having the following composition was prepared, and this 40% coating solution was applied to a dryer cylinder contact surface of Clupak paper with a dry weight of 15.0 g. / M ² and dried. Further, a base material for a craft adhesive tape finished to Oken type smoothness of 210 seconds by a super calendar was used. The results are shown in Table 1. Component Weight ・ 50% kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts ・ 50% styrene-butadiene copolymer latex (trademark: JSR0610, manufactured by Nippon Synthetic Rubber Industries) 20 parts ・ 20% oxidized modified starch (trademark) Prince Ace A, Prince Corn Starch) 3 copies

Example 3 In the same manner as in Example 1, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, instead of the silicone liquid of Example 1, a viscosity of 8
A silicone-based solventless release agent having a viscosity of 6 mPa (60 rpm B type viscosity) was used. The results are shown in Table 1.

Example 4 In the same manner as in Example 2, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, instead of the silicone liquid of Example 1, a viscosity of 8
A silicone-based solventless release agent having a viscosity of 6 mPa (60 rpm B type viscosity) was used. The results are shown in Table 1.

Comparative Example 1 A release paper was coated in the same manner as in Example 1 to produce a laminated paper simulating a kraft pressure-sensitive adhesive tape, and an evaluation test was performed. However, instead of the silicone liquid of Example 1, the viscosity 1
A silicone-based solventless release agent having a viscosity of 7 mPa (60 rpm B type viscosity) was used. The results are shown in Table 1.

Comparative Example 2 In the same manner as in Example 2, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, instead of the silicone liquid of Example 1, the viscosity 1
A silicone-based solventless release agent having a viscosity of 7 mPa (60 rpm B type viscosity) was used. The results are shown in Table 1.

Comparative Example 3 In the same manner as in Example 1, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, instead of the silicone liquid of Example 1, the viscosity 9
A silicone-based solventless release agent having a viscosity of 5 mPa (60 rpm B type) was used. The results are shown in Table 1.

Comparative Example 4 In the same manner as in Example 2, a release agent was applied, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, instead of the silicone liquid of Example 1, the viscosity 9
A silicone-based solventless release agent having a viscosity of 5 mPa (60 rpm B type) was used. The results are shown in Table 1.

Comparative Example 5 In the same manner as in Comparative Example 1, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, a 120 mesh roll was used instead of the 200 mesh gravure coater roll used in Comparative Example 1. The results are shown in Table 1.

Comparative Example 6 A release paper was applied in the same manner as in Example 3 to produce a laminated paper simulating a kraft adhesive tape, and an evaluation test was performed. However, in the preparation of the release paper of Example 1, a coating machine equipped with a Mayer bar was used instead of a coating machine equipped with a forward three roll offset gravure coater. The results are shown in Table 1.

Comparative Example 7 In the same manner as in Example 1, a release agent was coated, a laminated paper simulating a kraft adhesive tape was prepared, and an evaluation test was performed. However, in the preparation of the release paper of Example 1, a coating machine equipped with a Mayer bar was used instead of a coating machine equipped with a forward three roll offset gravure coater. The results are shown in Table 1. The results are shown in Table 1.

As is clear from Table 1, the release papers for kraft pressure-sensitive adhesive tapes of the examples according to the present invention each obtained satisfactory results, but the release papers of the comparative examples did not satisfy some properties. It was something.

[0034]

The method for producing a release paper for kraft pressure-sensitive adhesive tapes of the present invention comprises a base material having a polyethylene film layer having a thickness of about 10 to 25 microns formed on a surface of a clupak paper by a melt extrusion method. Regarding the production of release paper for kraft adhesive tape, which is a solvent-free silicone liquid coated as a release agent on a substrate having a dense barrier layer composed mainly of resin, etc., generated from Clupak paper in the coating process It can be easily manufactured by existing processing equipment without deteriorating quality and productivity due to paper powder to be produced, and is extremely excellent in practicality.

[0035]

[Table 1]

Claims (1)

[Claims] 1. A kraft stretch paper mainly made of wood pulp specified by JIS P3412-1976R, and formed on one surface of the kraft stretch paper and mainly composed of a polyethylene laminate layer or an aqueous resin. In a kraft pressure-sensitive adhesive tape release paper obtained by coating a kraft pressure-sensitive adhesive tape base material having a barrier layer with a release agent, the release agent is 20 to 90 mPa (60 rpm) at room temperature.
A method for producing a release paper for a kraft pressure-sensitive adhesive tape, comprising applying and crosslinking a silicone-based solvent-free release agent comprising a polyorganosiloxane having a B-type viscosity) using a forward three-roll offset gravure coater.