JP2000186258A - Production of kraft paper adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a kraft paper adhesive tape which does not affect the polyethylene based resin layer provided on the opposite side of a substrate in heating the adhesive tape to form fine cells in the adhesive layer and has the surface agreeable to the touch and also excels in the handling without curing of the adhesive tape in rewinding the roll-wound adhesive tape in use. SOLUTION: In the method for producing a kraft paper adhesive tape comprises laminating a polyethylene based resin layer on one side of a kraft paper, impregnating the opposite side of the kraft paper with water, then coating an adhesive thereon and heating the coated adhesive layer to form cells in the adhesive layer, the polyethylene based resin has a density of 0.925-0.950 g/cm3 and a melt flow rate of 1-20 g/10 min.

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 kraft paper adhesive tape.

[0002]

2. Description of the Related Art Kraft paper adhesive tapes are generally based on kraft paper having a low-density polyethylene film laminated on one side and a release agent layer provided on the low-density polyethylene film. It is provided with an adhesive layer and is suitably used for applications such as packing cardboard boxes. Of such kraft paper adhesive tape,
For example, a pressure-sensitive adhesive layer is foamed for the purpose of improving the adhesion to a rough adherend.

For example, Japanese Patent Publication No. 6-4827 discloses that
Melt index 8.0dg on one side of kraft paper
/ Min, density 0.919 g / cm^Three, Vicat softening point 87 ℃
Low-density polyethylene was laminated to a thickness of 15 μm.
Approximately 1 piece of methyl ethyl ketone with a boiling point of 80 ° C
0% by weight, and on the opposite side, styrene-isoprene
-Adhesive based on styrene block copolymer
Coat to a thickness of 30μm, then this tape
Is heated in a dryer at 85 ° C. for 10 minutes to count in the adhesive.
Manufacturing method of adhesive tape to form micro closed cells
Melt index instead of low density polyethylene coating
Is 24dg / min, density 0.90g / cm ^Three, Vicat softening
Thick polypropylene with a temperature of 151 ° C and a heat distortion temperature of 105 ° C
The tape base material laminated to a thickness of 25 μm is heated at 40 ° C. × 9
Stored in kraft paper for 50 hours in an atmosphere of 0% RH
After holding about 8% by weight of water, the adhesive was applied as above.
The tape is then dried in a dryer at 103 ° C. for 4 minutes.
Bonding by heating to form countless minute closed cells in the adhesive
A method for manufacturing a tape is disclosed.

However, in the case of a base material having a low-density polyethylene film provided on one surface of kraft paper, the vaporization pressure of the vaporizable substance that has diffused to the low-density polyethylene film side when the adhesive layer formed bubbles. Due to this, many irregularities and pinholes are generated on the low-density polyethylene film and deformed, and the surface (back surface) of the adhesive tape becomes rough and rough, which not only reduces the commercial value significantly, but also causes many irregularities and pinholes. In addition, the developing force for peeling off the wound adhesive tape was large and heavy, and in some cases, the base material layer and the adhesive layer were sometimes cracked.

When kraft paper laminated with polypropylene is used as a substrate, the so-called stiffness of the substrate becomes so strong that when the adhesive tape is used, the developed adhesive tape curls and the adhesive surfaces adhere to each other. In some cases, the handling efficiency may be significantly deteriorated, and the packing efficiency may be significantly reduced. Further, there is a problem that a substrate having a strong stiffness has a strong rebound when the cardboard box is sealed, and is easily peeled off. The repulsion at the time of sealing a cardboard box cannot be alleviated by using a flexible rubber for polypropylene or the like, but the flexible rubber is generally expensive and increases the cost.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to heat a pressure-sensitive adhesive tape to form fine air bubbles in a pressure-sensitive adhesive layer. It does not substantially affect the polyethylene resin layer provided on the opposite surface, has a good surface tactile sensation, and
An object of the present invention is to provide a method for producing a kraft paper adhesive tape which is excellent in handleability and does not curl when the wound adhesive tape is rewound and used.

[0007]

The method for producing a kraft paper pressure-sensitive adhesive tape according to the present invention comprises laminating a polyethylene resin layer on one side of kraft paper and impregnating the opposite side of the kraft paper with water. In the method for producing a kraft paper pressure-sensitive adhesive tape in which a pressure-sensitive adhesive composition is applied and heated to generate air bubbles in a pressure-sensitive adhesive layer, the density of the polyethylene resin is 0.925 to 0.925.
0.950 g / cm ³ , melt flow rate is 1 to 20
g / 10 minutes.

The kraft paper used for the base material layer in the present invention is not particularly limited as long as it is used for an adhesive tape, but is preferably a non-bleached kraft paper having a basis weight of 40 to 100 g / m ^2. Bleached kraft paper, bleached kraft paper, and the like can be mentioned. In particular, kraft paper subjected to clupak processing to impart elasticity to a base material is more preferably used.

When the density of the polyethylene resin laminated on one side of the kraft paper is less than 0.925 g / cm ³ , the heat resistance is not sufficient, and when the pressure-sensitive adhesive layer is heated to form fine bubbles, The polyethylene resin layer is also softened, bubbles enter and foam, and the obtained kraft paper pressure-sensitive adhesive tape surface has a rough touch and lowers commercial value. When the density exceeds 0.950 g / cm ³ , Since the so-called stiffness of the polyethylene resin layer becomes too strong, the resulting kraft paper adhesive tape tends to curl and warp, which deteriorates the handleability and lowers the work efficiency such as cardboard box packing work. It is limited to the above range.

The melt flow rate (hereinafter abbreviated as MFR) of the polyethylene resin is JIS K72.
When the value is less than 1 g / 10 minutes, the moldability is poor, processing such as laminating the thin film is difficult, and the productivity is particularly lowered.
If the heating time exceeds 10 minutes, the heat resistance is reduced, and the foam may be foamed due to softening during the formation of the above-mentioned bubbles.

The polyethylene resin has the above-mentioned density and MF
If it is in the range of R, low density polyethylene,
Medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer mainly composed of ethylene, ethylene-α-olefin copolymer,
Any polyethylene resin such as an ethylene-vinyl acetate copolymer or an ethylene-acrylate copolymer can be arbitrarily selected and used. These polyethylene resins may be used alone or in combination of two or more. Various additives such as a colorant and an antioxidant may be added to the polyethylene resin as needed without departing from the spirit of the present invention.

Means for providing a polyethylene resin layer on one surface of kraft paper is not particularly limited, but for example, extrusion lamination is preferred because of high productivity and strong adhesive strength to base kraft paper. Used for The polyethylene resin layer in the extrusion lamination method may be a single layer, or may be a composite film layer of two or more layers. The thickness of these polyethylene resin layers is not particularly limited, but is preferably 10 to
25 μm.

[0013] A release layer may be provided on the polyethylene resin layer to facilitate peeling of the wound adhesive tape. Usually, the release layer is provided before forming the pressure-sensitive adhesive layer, and it is necessary to withstand heating during foaming of the pressure-sensitive adhesive layer. Therefore, examples of the release agent include an addition reaction type silicone resin-based release agent and a condensation reaction type silicone resin-based release agent. Is preferably used, and as a means for forming the release layer, a coating method using a gravure roll or the like is suitably used.

Means for impregnating the kraft paper as the base material with water is not particularly limited, and examples thereof include a transfer coating method using a gravure roll or the like and a spray method using a spray or the like.

The pressure-sensitive adhesive used in the present invention is not particularly limited, and examples thereof include a natural rubber-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, and a thermoplastic elastomer-based pressure-sensitive adhesive. Above all, it is easily softened by heating,
A thermoplastic elastomer-based pressure-sensitive adhesive that does not hinder the gasification of water, cools and solidifies, finely disperses and holds formed bubbles, and exhibits favorable buffering properties is preferably used. The means for applying the pressure-sensitive adhesive is not particularly limited, and examples thereof include an application method using a roll coater, a die coater or the like.

The means for heating the pressure-sensitive adhesive tape for generating air bubbles in the pressure-sensitive adhesive layer is not particularly limited. For example, a heating and drying device for a pressure-sensitive adhesive tape using a solvent-type pressure-sensitive adhesive is usually used.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Embodiment) A polyethylene resin (density 0.935 g / cm ³ , MFR = 7.0 g / 1) was applied to one side of unbleached kraft paper (basis weight 75 g / m ² ) which had been subjected to clupak processing.
0 minutes) by extrusion lamination to a thickness of 20 μm, and further, an addition-reaction type silicone resin-based release agent on the polyethylene-based resin laminate layer to a solid content of 0.6 g / m ^2. To form a release layer.

After spray-coating water on the other side of the unbleached kraft paper with a spray so as to have a coating amount of 4 g / m ² , a styrene-isoprene-styrene block copolymer (trade name, manufactured by Shell Co., Ltd.) "TR-1107") 100 parts by weight, petroleum resin (manufactured by Zeon Corporation, trade name "Quinton A"
-100 "), 30 parts by weight of process oil (manufactured by Shell Co., trade name" Shellflex 702 ") and an antioxidant (manufactured by Yoshitomi Pharmaceutical Co., Ltd., trade name" Yoshinox 4 ")
25 ") 1 part by weight of a thermoplastic elastomer-based pressure-sensitive adhesive composition was melt-extruded and coated using a die coater so that the coating amount was 40 g / m ^2, and heated in a 160 ° C. oven for 30 seconds for adhesion. A kraft paper adhesive tape in which bubbles were generated in the agent layer was produced. The obtained kraft paper pressure-sensitive adhesive tape has an extremely good number of bubbles generated in the pressure-sensitive adhesive layer, is uniform and does not substantially affect the polyethylene-based resin laminate layer, and is extremely good. It had a surface feel.

Comparative Example 1 A polyethylene resin (density 0.923 g / cm ³ , MFR = 5.0 g / 10) was used in place of the polyethylene resin in the extruded laminate layer of Example 1.
Kraft paper pressure-sensitive adhesive tape was produced in the same manner as in Example, except that the above-mentioned Example 1) was used. In the obtained kraft paper adhesive tape, bubbles generated during foaming of the adhesive layer form through holes and irregularities in the polyethylene resin laminate layer through the kraft paper, and have a poor surface (back) tactile sensation. there were.

Comparative Example 2 A polyethylene resin (density 0.960 g / cm ³ , MFR = 8.0 g / 10) was used instead of the polyethylene resin of the extruded laminate layer of Example 1.
Kraft paper pressure-sensitive adhesive tape was produced in the same manner as in Example, except that the above-mentioned Example 1) was used. The obtained kraft paper pressure-sensitive adhesive tape was curled at the time of application of the pressure-sensitive adhesive layer because the stiffness of the polyethylene resin laminate layer was too strong, and was extremely poor in handleability when used.

In order to evaluate the performance of the kraft paper pressure-sensitive adhesive tapes of Examples and Comparative Examples 1 and 2, the degree of curl, the state of foaming of the polyethylene resin laminate layer, and the tactile sensation of the polyethylene resin laminate layer were determined by the following methods. evaluated.
Table 1 shows the results.

Evaluation method (degree of curl) A 1 mm kraft paper adhesive tape having a width of 50 mm was pulled out, hung vertically, visually observed, and those which hung vertically without hardly curling were regarded as good (（).
Curling and adhesion between the pressure-sensitive adhesive layers and the danger of the adhesion were evaluated as poor (x).

(Number of Foams in Laminated Layer) The foaming state of the laminated layer was randomly selected from five points of 5 mm × 4 mm area by a microphotograph (magnification: 20) analysis method, and the number of foams in the laminated layer was counted from the micrograph. The average value of 5 points was calculated. The foaming state of the laminate layer and the feel of the kraft paper pressure-sensitive adhesive tape surface (rear surface) were determined by using a separately manufactured kraft paper pressure-sensitive adhesive tape. ) Has been correlated with a good feel.

(Tactile sensation of the laminate layer) Kraft paper adhesive tape having a width of 50 mm is placed on a flat backing paper with an adhesive layer having a length of 20 c.
m, the sensory test of the hand feeling of the laminate layer
Those giving a smooth and good tactile sensation were evaluated as good (O), and those giving a rough and unpleasant tactile sensation were evaluated as poor (x).

[0026]

[Table 1]

[0027]

Since the method for producing a kraft paper pressure-sensitive adhesive tape of the present invention is constituted as described above, air bubbles formed finely and uniformly in the pressure-sensitive adhesive layer are formed on the polyethylene resin laminate layer on the back surface. The present invention is capable of producing a kraft paper pressure-sensitive adhesive tape having excellent performance without deteriorating tactile sensation or curling the pressure-sensitive adhesive tape and deteriorating handleability, at high speed and with high productivity.

Claims (1)

[Claims] 1. A kraft paper is laminated with a polyethylene resin layer on one side and impregnated with water on the other side, and then coated with an adhesive composition and heated to generate air bubbles in the adhesive layer. In the method for producing a kraft paper adhesive tape, the density of the polyethylene resin is 0.925 to 0.950 g / cm.
^{3. A} method for producing a kraft paper adhesive tape, wherein the melt flow rate is 1 to 20 g / 10 minutes.