Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-03-27
2002-07-02
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S509000, C524S481000, C524S270000, C525S098000, C525S285000
Reexamination Certificate
active
06414073
ABSTRACT:
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to a pressure-sensitive adhesive material and more particularly to a pressure-sensitive adhesive material useful for applications involving immersion in an aqueous liquid such as water, ink or alkali in a state where an adherend is adhered thereto.
2. DESCRIPTION OF THE RELATED ART
Sometimes the adherend to which a pressure-sensitive material is adhered is contacted with or immersed in aqueous liquids such as water, aqueous solution or aqueous dispersion. For example, in the process of dyeing fabric, the fabric is bonded to a stainless steel plate or iron plate with a pressure-sensitive adhesive double-coated tape before it can be immersed in an aqueous solution of a dye. Also, in the process of polishing silicon wafers, liquid crystal glasses, etc., a pad carrying abrasive slurry called abrasive cloth is used by bonding it to a mechanical surface plate with a pressure-sensitive adhesive double-coated tape. In this case, during the polishing, the pressure-sensitive adhesive layers of the pressure-sensitive adhesive double-coated tape are exposed to an aqueous liquid in which abrasive is dispersed. (3) In these applications, the pressure-sensitive adhesive material of the pressure-sensitive adhesive double-coated tape must be peeled off again from the stainless steel plate, iron plate, or mechanical surface plate after use. For this purpose, films made of polyethylene terephthalate (PET) or the like material that has high strength as the backing and the pressure-sensitive adhesive layer must have cohesion or anchoring power to the backing in the case of the pressure-sensitive adhesive double-coated tape. In some cases, a backing-less, pressure-sensitive adhesive tape is applied in advance only to a necessary portion of a film such as PET film to transfer a pressure-sensitive adhesive layer to the film and the resulting film is used by laminating it on various members.
In such a pressure-sensitive adhesive material, use of acrylic pressure-sensitive adhesive as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer tends to give some cohesion or anchoring power to the backing but because of its high water absorption, its cohesion and anchoring power decreases when it is immersed in aqueous liquids and the pressure-sensitive adhesive remains on the adherend. In the case of acrylic pressure-sensitive adhesives, a time-dependent increase in adhesion is disadvantageous to removability.
In the case where synthetic rubber such as styrene-butadiene-styrene block copolymer (SBS) or the like is used as the pressure-sensitive pressure adhesive constituting the pressure-sensitive adhesive layer, adjustment of cohesion by the styrene content of the synthetic rubber can give anchoring power to PET or the like with ease. However, such a pressure-sensitive adhesive has high elastic modulus so that it cannot gain broader adhesion area at its true interface when it is applied, with the result that water invades at the interface during immersion in the aqueous liquid to thereby decrease its adhesion to the adherend.
Furthermore, the natural rubber-based pressure-sensitive adhesives are best in view of low water absorption and low time-dependent increase in adhesion. However, natural rubbers have low anchoring powers to PET so that adhesion facilitation treatment such as provision of undercoat is needed. However, such means is still insufficient.
On the other hand, in some of the above-mentioned applications, presence of metal ions is undesirable. For example, in the process of polishing silicon wafers, there is the possibility that metals ions such as Mg, Al, Ca, Fe, Ni, Cu, Zn, Cr, Zr, Ti, etc. could cause failures in subsequent circuit formation step. Also, in the process of dyeing fabrics, metal ions cause agglomeration of dyestuff or pigment, occasionally forming uneven dyeing or precipitation
In the case of natural rubber-based pressure-sensitive adhesives, use is made of Zn, Ca, Mg, Al, S, etc. or oxides thereof as a filler or crosslinking agent to exhibit cohesion. In the above-mentioned applications, the cohesion of pressure-sensitive adhesive is a very important factor. However, use of metals or metal oxides has the possibility of causing problems as explained above. Accordingly, crosslinking with polyisocyanates, crosslinking with phenol resins, and crosslinking with peroxides have been studied. The crosslinking with polyisocyanates tends to impart sufficient anchoring power to the pressure-sensitive when the backing is made of PET but when it is immersed in water, it undergoes hydrolysis, resulting in that the cohesion tends to decrease. The crosslinking with the phenol resin requires high temperatures and if the pressure-sensitive adhesive is directly to the backing, the backing of film may sometimes be deformed. When the pressure-sensitive adhesive coated on a release liner is applied to a backing to transfer the adhesive, the pressure-sensitive adhesive has low anchoring power to the backing and no desirable result can be obtained. Further, to effect reaction at low temperatures, it is necessary to use complexes of phenol resins with Mg, Ca, etc. However, these cannot be used in applications where metal ions are undesirable. Use of the crosslinking with peroxides is accompanied by the danger upon production, causes an odor to remain in the pressure-sensitive adhesive or the residue to undergo deterioration per day.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a pressure-sensitive adhesive material that sufficiently exhibits cohesion of the pressure-sensitive adhesive layer and anchoring power to the backing and that maintains the cohesion and anchoring power when immersed in an aqueous liquid without compounding a metal or metal compound.
With view to achieving the above object, the present inventors have made intensive research and as a result they have found that construction of the pressure-sensitive adhesive layer from a pressure-sensitive adhesive comprising natural rubber and a specified styrene-isoprene-styrene block copolymer (SIS) in a specified ratio not only gives rise to excellent cohesion and anchoring power but also maintains the cohesion and anchoring power when it is contacted with or immersed in water in a state where an adherend is attached. The present invention has been accomplished based on this discovery.
That is, the present invention provides a pressure-sensitive adhesive material comprising a pressure-sensitive adhesive layer comprising 100 parts by weight of natural rubber and 10 to 120 parts by weight of styrene-isoprene-styrene block copolymer (SIS) having a radiate configuration with a styrene content of 10 to 45% by weight.
In a first aspect, the present invention provides a pressure-sensitive adhesive material comprising a pressure-sensitive adhesive layer comprising 100 parts by weight of natural rubber and 10 to 120 parts by weight of styrene-isoprene-styrene block copolymer (SIS) having a radiate configuration with a styrene content of 10 to 45% by weight.
Here, the pressure-sensitive adhesive layer is preferably free of metals or metal compounds.
The pressure-sensitive adhesive layer may contain a resin having an acid value of 1.5 or more in an amount of 5 to 150 parts by weight as a tackifier.
The resin having an acid value of 1.5 or more as a tackifier may be a maleic anhydride-modified resin.
The pressure-sensitive adhesive material may be a backing-less tape that comprises a release liner and the pressure-sensitive adhesive layer on a surface of the release liner.
The pressure-sensitive adhesive material may be a pressure-sensitive adhesive double-coated tape having pressure-sensitive adhesive layers on respective surfaces thereof, at least one of which is constituted by the pressure-sensitive adhesive layer.
The pressure-sensitive adhesive material may be used in the presence of an aqueous liquid.
In a second aspect, the present invention provides a method for adhesion using a pressure-sensiti
Amano Tatsumi
Harada Chiaki
Nakamura Koichi
Shibata Kazuhiko
Yamamoto Hiroshi
Asinovsky Olga
Kilyk & Bowersox P.P.L.C.
Nitto Denko Corporation
Seidleck James J.
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