JP2002220572A - Releasable adhesive sheet and sanitary goods using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet having a proper initial adhesive strength to an adherend, hardly causing change of the adhesive strength with time, hardly causing adhesive transfer or breakage of the adherend or the substrate of the adhesive sheet, and capable of being repeatedly stuck and removed, and further to provide sanitary goods using the adhesive sheet as a fastener for a singly packaging bag. SOLUTION: This adhesive sheet has an adhesive agent layer comprising 35-75 wt.% radial styrene-isoprene-styrene block copolymer having three or more terminal styrene polymer blocks, and 25-65 wt.% adhesion-imparting resin of which 15-80 wt.% is the adhesion-imparting resin liquid at normal temperature, and has a 180 deg. peeling strength at 3-20 m/min peeling rate regulated so that the 180 deg. peeling strength may be increased according to the increase of the peeling rate when peeling the adhesive sheet from the adherend. The sanitary napkin uses the adhesive sheet as the fastener for the singly packaging bag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet which shows a high initial adhesive strength to an adherend and which can be peeled off and re-adhered after a lapse of time, and the pressure-sensitive adhesive sheet is used for stopping individual packaging. Related to sanitary napkins.

[0002]

2. Description of the Related Art There are two uses of a pressure-sensitive adhesive sheet: one is that the adherend itself is not peeled off after it is attached to the adherend, and the other is that peeling and re-adhesion are repeated as necessary.
Examples of the latter include product labels and tags that are adhered and fixed to products displayed at storefronts, adhesive tapes for sealing product packaging bags, fastening tapes for disposable diapers, and adhesives for stopping individual packaging bags on sanitary napkins. There are tapes and the like, and the material of the adherend covers a wide variety such as plastic films, woven fabrics, non-woven fabrics and paper. Conventional pressure-sensitive adhesive sheets used for such applications, the adherend or the pressure-sensitive adhesive sheet substrate will break when peeling due to too strong adhesion, or the pressure-sensitive adhesive remains on the adherend There are some types of adhesives (adhesive residue) and, on the contrary, those that have too low adhesive strength and peel off. Especially when the adherend is a product, its commercial value is impaired. However, there is a demand for a pressure-sensitive adhesive sheet which has little change over time in adhesive force, does not leave adhesive residue or breakage of an adherend or a pressure-sensitive adhesive sheet substrate during peeling, and can be re-adhered.

[0003] In particular, when an adhesive sheet is used to stop an individual wrapping bag of a sanitary napkin, the adhesive strength to an adherend increases with time after application, and the individual wrapping bag expands when used by consumers. There have been problems such as breakage, breakage, and the fact that the adhesive remains and contaminates the adherend. Conversely, if the adhesive force is too weak, in the manufacturing stage of the sanitary napkin, the adhesive sheet may be peeled off in the process of packing the individual wrapping bag of the sanitary napkin, or when the consumer discards after use, There was a problem of not re-adhering. As a solution to the above problem, Japanese Patent No. 2981143 discloses an adhesive sheet in which the adhesive force to an adherend decreases as the peeling speed increases. However, such an adhesive sheet has a small increase in adhesive strength after aging and is hard to be broken, but has a low initial adhesive strength to the adherend and peels off. The sticking phenomenon (peeling off of the jerky) causes the adhesive sheet to be broken, resulting in poor re-adhesiveness and poor appearance.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an adhesive material having an appropriate initial adhesive force, a small variation in adhesive force with time, and a problem of adhesive residue and coating when peeled off with time. It is an object of the present invention to provide a pressure-sensitive adhesive sheet that can be repeatedly re-adhered and re-peeled without breaking a body or a pressure-sensitive adhesive sheet substrate, and a sanitary product using the pressure-sensitive adhesive sheet for individual packaging bag closure.

[0005]

Means for Solving the Problems The present inventors have found that the pressure-sensitive adhesive layer contains 35 to 75% by mass of a radial styrene-isoprene-styrene block copolymer having three or more terminal styrene polymer blocks, 25-65% by mass of applied resin
And 15 to 80% by mass of the tackifier resin is a liquid tackifier resin at room temperature, and 180 at a peeling speed of 3 to 20 m / min when the pressure-sensitive adhesive sheet is peeled from the adherend. ° The above problem was solved by providing a pressure-sensitive adhesive sheet in which the peeling force increases as the peeling speed increases, and by providing a sanitary napkin using the pressure-sensitive adhesive sheet for individual packaging bag closure.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present specification, without adhesive residue on the adherend, without breaking the adherend or the pressure-sensitive adhesive sheet substrate, to easily peel the adhesive sheet from the adherend is referred to as "re-peeling", The ability to be re-peelable is called "re-peelability".

The pressure-sensitive adhesive sheet of the present invention is characterized in that when peeled from an adherend, the 180 ° peeling force (ie, adhesive force) at a peeling speed of 3 to 20 m / min increases as the peeling speed increases. When the peeling speed of the pressure-sensitive adhesive sheet is increased, the lower the elasticity of the pressure-sensitive adhesive layer and the softer the pressure, the greater the deformation of the pressure-sensitive adhesive layer and the higher the adhesive strength. To lower or soften the elasticity of the pressure-sensitive adhesive layer, add or increase the amount of liquid tackifying resin at room temperature, reduce the amount of solid tackifying resin at room temperature, or apply solid tackifier at room temperature with a low softening point temperature. Using a resin, using a styrene-isoprene-styrene block copolymer having a small molecular weight, using a styrene-isoprene-styrene block copolymer having a low styrene content in a terminal styrene block, and using a styrene having a small coupling ratio. Such as using an isoprene-styrene block copolymer.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present invention comprises:
It contains a styrene-isoprene-styrene block copolymer, a tackifier resin, and a tackifier resin that is liquid at room temperature. The styrene-isoprene-styrene block copolymer used in the present invention is not particularly limited except that it is a radial styrene-isoprene-styrene block copolymer having three or more terminal styrene polymer blocks. . The styrene-isoprene-styrene block copolymer has a structure in which a flexible isoprene block is fixed from both ends by hard styrene blocks.
Therefore, since the structure having a larger number of terminal styrene blocks more restricts the flexible isoprene block, it is possible to suppress the wetting of the pressure-sensitive adhesive to the adherend due to the isoprene block. As a result, an increase in the adhesive force with time is suppressed, and the adherend or the pressure-sensitive adhesive sheet substrate can be peeled off without breaking even after time.

The molecular weight of the styrene-isoprene-styrene block copolymer is preferably in the range of 10,000 to 800,000. If it is less than 10,000, the cohesive strength of the pressure-sensitive adhesive decreases, and the increase in the adhesive force with time increases, causing breakage of the adherend, or when repeatedly adhering to the adherend, or when peeling off after a lapse of time. Glue residue occurs. On the other hand, if it exceeds 800,000, the modulus of elasticity becomes too high, and the adhesion to the adherend deteriorates, so that a sufficient initial adhesive strength cannot be obtained.

[0010] The styrene content of the terminal styrene block of the styrene-isoprene-styrene block copolymer is preferably about 10 to 50% by mass. If the amount is less than 10% by mass, the pressure-sensitive adhesive will greatly wet the adherend due to isoprene, and the adhesive force will increase significantly with time, causing breakage of the adherend. On the other hand, at 50% by mass or more,
Since the elastic modulus of the pressure-sensitive adhesive is too high, the adhesion to the adherend is deteriorated, and a sufficient initial adhesive strength cannot be obtained.

The coupling ratio of the styrene-isoprene-styrene block copolymer (mass ratio to the total blocks of the triblock; triblock has a styrene-isoprene-styrene structure) is 5
The content is preferably 0% by mass or more. When the coupling ratio is less than 50% by mass, the cohesive force of the pressure-sensitive adhesive is reduced, the wettability to the adherend is increased, and the increase in adhesive force over time is increased, and the adherend is torn. Adhere to adherend, or
When re-peeling after lapse of time, adhesive residue may be generated.

As specific examples of such a styrene-isoprene-styrene block copolymer, for example, "Quintac 3450" (number of styrene polymer blocks 3 to 4) and "Quintac 3460" manufactured by Zeon Corporation
(The number of terminal styrene polymer blocks is 3 to 4), and “Clayton D1124” (manufactured by Shell Chemical Co., Ltd.) (the number of terminal styrene polymer blocks is 3 to 4).

As the tackifier resin used in the present invention, a solid resin and a liquid resin at room temperature are used in combination. For the purpose of suppressing the increase of the adhesive force over time and securing the initial adhesiveness, it is preferable that the adhesive is given an appropriate cohesive force or elasticity. When the tackifying resin is solid, its softening point is 6
It is preferably about 0 to 140 ° C, more preferably 90 to 120 ° C. Further, the tackifier resin is preferably a resin having compatibility with the isoprene block. As a result, the initial adhesion to the adherend is improved, the target adhesion is obtained with a small amount of addition, and the increase of the adhesion over time is suppressed. Specific examples of such a tackifying resin include C5 petroleum resin, alicyclic petroleum resin, alicyclic / aromatic petroleum resin, terpene resin, rosin resin, rosin ester resin, terpene-phenol. Resins, alkylphenol resins and the like. A small amount of a styrene block-compatible resin such as an aromatic resin may be added in order to improve the cohesive force of the pressure-sensitive adhesive and suppress the increase in the adhesive force over time.

The proportion of the tackifier resin is preferably 25 to 65% by mass of the whole pressure-sensitive adhesive, and particularly preferably 30 to 60% by mass. When the amount is less than 25% by mass, the adhesion to the adherend is deteriorated, and the adhesive may be peeled off from the adherend during initial bonding or over time. On the other hand, the addition ratio is 65% by mass.
When it exceeds, the adhesive strength to the adherend becomes large, and there is a possibility that the adherend may be broken at the time of peeling immediately after application or after elapse of time.

A tackifier resin which is liquid at room temperature is added to the pressure-sensitive adhesive of the present invention. Examples of the tackifying resin which is liquid at ordinary temperature include C5 petroleum resin, alicyclic petroleum resin, alicyclic / aromatic petroleum resin, terpene resin, rosin resin, rosin ester resin, terpene-phenol resin, Examples thereof include an alkylphenol resin, a process oil, a polyester-based plasticizer, liquid polybutene, liquid polypentane, and liquid polyisobutylene. The ratio of the tackifier resin which is liquid at normal temperature to the total amount of the tackifier resin is 15 to 80% by mass.
Is preferably, and particularly preferably 20 to 70% by mass. If the amount is less than 15% by mass, the pressure-sensitive adhesive will have poor wettability to the adherend, and peeling may occur due to a decrease in the initial adhesive force. On the other hand, when the content exceeds 80% by mass, the cohesive force of the pressure-sensitive adhesive decreases, and there is a possibility that adhesive residue may be generated when the pressure-sensitive adhesive is repeatedly adhered to an adherend or peeled off after a lapse of time. There is a possibility that the adherence to the adherend is excessively increased due to penetration into the unevenness of the body surface and the adherend is broken.

In the present invention, a crosslinking agent may be used if necessary, and various additives generally used for an adhesive, for example, an antioxidant, an ultraviolet absorber, a filler,
A pigment, a thickener, and the like may be added in a range where the adhesive strength is not reduced.

In order to form a pressure-sensitive adhesive layer on a support film serving as a pressure-sensitive adhesive sheet substrate, the above-mentioned styrene-isoprene-styrene block copolymer, tackifying resin, liquid-state tackifying resin at room temperature, and Accordingly, various additives may be mixed and dissolved in an organic solvent such as toluene or xylene for application, or the mixture may be heated and melted for application. The pressure-sensitive adhesive may be directly applied to the support film, or may be applied on a separator, dried, and then bonded to the support film. According to the above method, a pressure-sensitive adhesive layer is provided on a surface of the support film having a release agent layer on one side, as required, opposite to the release agent layer. Usually, a separator is stuck to the pressure-sensitive adhesive layer to form a sheet. However, when the support film is provided with a release agent layer, it can be wound into a roll without using the separator. The thickness of the pressure-sensitive adhesive layer is preferably from 10 to 100 μm. When it is used for stopping individual sanitary napkins, the thickness is particularly preferably 15 to 50 μm.

The support film is not particularly limited, and examples thereof include a plastic film such as a polypropylene film, a polyethylene film, a polyester film and a polyvinyl chloride film, and a porous support such as a nonwoven fabric, cloth and paper. . Preferably, a single-layer or multilayer plastic film mainly composed of polypropylene is used. The surface may be flat or matte. The thickness of the support film is preferably from 5 to 200 μm. In order to improve the adhesion between the pressure-sensitive adhesive layer and the release agent layer, the surface of the support film is preferably subjected to a corona treatment or a primer treatment.

The pressure-sensitive adhesive sheet of the present invention is characterized in that when peeled from an adherend, the 180 ° peeling force (that is, adhesive force) at a peeling speed of 3 to 20 m / min increases as the peeling speed increases. This feature, when the adhesive sheet of the present invention is used for individual wrapping of sanitary napkins,
When packing individual packages of sanitary napkins in the manufacturing process, an effect of preventing the adhesive sheet from being peeled off by an instantaneous force (high-speed peeling force) is exhibited. In addition, when using a sanitary napkin, it is possible to prevent the root portion of the pressure-sensitive adhesive sheet affixed to the individual wrapping bag from peeling at a high speed. 180 ° to the adherend of the adhesive sheet
If the peeling force (adhesive force) is too weak, it will peel off from the adherend, and if the adhesive force is too strong, the re-peelability will decrease, so the adhesive force is desirably 1 to 15N. further,
In the pressure-sensitive adhesive sheet of the present invention, the slip stick phenomenon (jerky peeling) does not easily occur when peeled off, and the pressure-sensitive adhesive sheet does not have any fold marks. For this reason, when the used sanitary napkin is put into an individual bag and discarded, there is an advantage that the re-adhesiveness is good and the adhesive sheet does not peel off.

The pressure-sensitive adhesive sheet of the present invention is not limited to the material of the adherend, and may be, for example, a plastic film such as a polypropylene film, a polyethylene film, a polyester film, a polyvinyl chloride film, or a basis weight of 5 to 200.
g / m ² , a porous adherend such as a woven fabric, a nonwoven fabric, and a paper. As the sanitary napkin packaging bag, a thin, soft, low tensile strength adherend such as a plastic film, for example, a polyethylene film or a polypropylene film having a thickness of 20 to 50 μm is used. The pressure-sensitive adhesive sheet of the present invention is particularly effectively used for such an adherend having a thickness of 5 to 200 μm, which is soft and has low tensile strength.

Suitable uses of the pressure-sensitive adhesive sheet of the present invention other than the above-mentioned sanitary napkin include labels for clothes, tags, sealing materials for packaging bags, fastening tapes for disposable diapers,
There are re-peelable labels for sticky notes.

[0022]

The present invention will be described more specifically below with reference to examples and comparative examples. Unless otherwise noted,
“Parts” and “%” mean “parts by mass” and “% by mass”, respectively.

(Example) Styrene-isoprene-styrene block copolymer 100 parts (coupling ratio 70%, styrene content 30% by mass, number of terminal styrene blocks 3 to 4) Petroleum resin (number average molecular weight 1250, softening point) 101 ° C) 60 parts Liquid polypentane (“Marca Clear H” manufactured by Maruzen Petrochemical Co.) 50 parts The above adhesive resin and tackifier resin are dissolved in toluene,
An adhesive solution having a nonvolatile content of 50% was prepared. This solution was dried using an applicator to a thickness of 30 μm after drying.
m, coated on 40 μm thick biaxially oriented polypropylene (OPP), dried at 80 ° C. for 3 minutes,
An adhesive sheet was prepared by laminating the adhesive sheet with a separator.

Comparative Example Styrene-isoprene-styrene block copolymer 100 parts (coupling ratio 70%, styrene content 30% by mass, number of terminal styrene blocks 3 to 4) Petroleum resin (number average molecular weight 1250, softening point) (101 ° C.) 80 parts An adhesive sheet was produced in the same manner as in Example 1, except that the composition of the adhesive resin and the tackifier resin was changed as described above.

The adhesive sheets prepared in Examples and Comparative Examples were adhered to a polyethylene film having a thickness of 30 μm, and the initial adhesive force, the adhesive force with time after leaving at 60 ° C. for 3 days, and the adhesive force by peeling speed were measured. The results were evaluated according to the following criteria. Further, the sanitary napkin was adhered and fixed to an individual packaging bag made of polyethylene film having a thickness of 30 μm with an adhesive sheet prepared in Examples and Comparative Examples, and in a practical test, initial adhesion, tape detachment, breakage of the adherend, and The re-adhesion was tested and the results were evaluated according to the following criteria. Table 1 shows the test results and the evaluation results.

[Adhesive Strength] The following adhesive strength was measured using a 30 μm thick polyethylene film as an adherend. <Initial adhesive strength> An adhesive sheet having a width of 25 mm was adhered to an adherend at 23 ° C. and 65% RH under 2 kg × 1 reciprocating pressure, and immediately thereafter, a T-shaped peeling force was applied at a pulling speed of 300 mm / min, that is, initial adhesive strength. The force was measured. <Adhesion over time> Under the same conditions as the initial adhesive force, a 25 mm-wide adhesive sheet was attached to the adherend, left at 60 ° C. for 3 days, and then subjected to a T-type peeling force at a tensile speed of 300 mm / min. The adhesive force over time was measured. <Dependence of adhesive force on tensile speed> A 25 mm wide adhesive sheet was stuck to an adherend under the same conditions as the initial adhesive force,
After leaving for 1 hour under the following conditions, a 180 ° peeling force, that is, an adhesive force was measured at a predetermined pulling speed. [Practical test] <Initial adhesiveness> The finger-sensitive adhesiveness immediately after sticking to an individual packaging film was evaluated. ：: Just good, × 1: Too weak, × 2: Too strong <Tape detachment> The detachment of the pressure-sensitive adhesive sheet after sticking to an individual wrapping film and left at 60 ° C. for 3 days was evaluated. ：: no detachment, ×: detachment <Tear> The individual wrapping film was affixed to the individual wrapping film, and after being left at 60 ° C. for 3 days, the individual wrapping film was evaluated for tearing. ：: No tear, ×: There was tear <Re-adhesiveness> The finger-feeling re-adhesiveness of the sample subjected to the above <Tear> test was evaluated. ：: just good, × 1: too weak, × 2: no adhesion (film tear)

[0027]

[Table 1]

From the results shown in Table 1, it can be seen that the pressure-sensitive adhesive sheet of the present invention has a sufficient initial adhesive strength to the adherend, has little variation in the adhesive force with time, and has a small Alternatively, the adhesive sheet substrate can be repeatedly re-adhered and re-peeled without breaking.

[0029]

The pressure-sensitive adhesive sheet of the present invention has a sufficient initial adhesive force to an adherend, has little variation in adhesive force with time, and has been peeled off with time, which could not be achieved by the prior art. When the adherend or the adhesive sheet substrate is not broken,
And it has the effect that re-adhesion and re-peeling are possible repeatedly. In particular, when the pressure-sensitive adhesive sheet is used as a pressure-sensitive adhesive tape for stopping individual wrapping of a sanitary napkin, even when the plastic film as the adherend is thin and has low tensile strength, it has a sufficient initial adhesive strength, and When peeling after a lapse of time, the adherend or the pressure-sensitive adhesive sheet substrate can be repeatedly peeled off and re-bonded without breaking.

Claims (2)

[Claims] 1. A styrene-isoprene-radiation wherein the pressure-sensitive adhesive layer has three or more styrene-terminated polymer blocks.
It contains 35 to 75% by mass of a styrene block copolymer and 25 to 65% by mass of a tackifier resin, and 15 to 80% by mass of the tackifier resin is a liquid tackifier resin at room temperature,
Further, the pressure-sensitive adhesive sheet is characterized in that the 180 ° peeling force at a peeling speed of 3 to 20 m / min when the pressure-sensitive adhesive sheet is peeled from the adherend increases as the peeling speed increases. 2. A sanitary napkin using the pressure-sensitive adhesive sheet according to claim 1 for stopping individual packaging bags.