Abrasive tool making process – material – or composition
Patent
1994-11-28
1997-07-15
Lipman, Bernard
Abrasive tool making process, material, or composition
515103, 515281, 515293, 515300, 515301, 515305, 5153282, 5153292, 5153294, 5153297, 5153298, 5153299, 5153301, 5153592, 515375, 515383, C08F 830
Patent
active
056484259
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a permanently removable, low melt viscosity acrylic pressure-sensitive adhesive. In particular, the present invention relates to an adhesive comprising a lower alkyl acrylate, a higher alkyl acrylate, a polar monomer and a crosslinker.
BACKGROUND OF THE INVENTION
Removable pressure sensitive adhesives (PSA) adhered to a backing, which predictably adhere, yet remain repeatedly peelable from a variety of substrates over a long period of time without damaging or marring the substrate, have many commercial uses. For example, masking tapes, removable labels or office notes, protective films and medical tapes all must quickly adhere to metal, paper, plastics and skin, respectively, but must also peel smoothly away from these varied substrates without leaving behind any adhesive residue on or damaging the surface of a particular substrate.
Ideally, depending on the substrate, the removable adhesive must provide sufficient tack (or quick stick) to quickly fix the adhesive to the desired substrate, adequate peel strength to prevent damage of the surface when the adhesive is removed, and have the appropriate cohesive strength to control the transfer of adhesive to the substrate. Cohesive strength must also be controlled in order to limit the cold flow of the adhesive on a surface, a process which leads to an undesirable building of peel strength over time. Balancing these pressure sensitive adhesive properties, particularly in a removable adhesive, poses difficulties to the formulator.
U.S. Pat. No. 3,691,140 (Silver) discloses the use of solid, inherently tacky, pressure-sensitive adhesive microspheres which, when adhered to a first substrate, may when contacted to a second substrate be easily removed from the second substrate without delaminating the first substrate or the second substrate. While exhibiting a high degree of removability, microsphere adhesives tend to transfer to contact surfaces such as the second substrate.
U.S. Pat. No. 5,045,569 (Delgado) discloses hollow, inherently tacky pressure-sensitive adhesive acrylate microspheres which, due to their unique morphology, provide enhanced peel and shear strength and less adhesive transfer to substrates than "repositionable" adhesives based on solid acrylate-based microspheres.
U.S. Pat. No. 4,599,265 (Esmay) discloses an adhesive having a high degree of cohesive strength. The adhesive disclosed is an acrylate, has low tack and maintains peelability from a variety of ordinary substrates. Esmay teaches that through the crosslinking of the tape's adhesive layer and the use of low levels of polar monomer (up to 3 mole percent of a strongly polar monomer, such as acrylic acid) along with alkyl acrylates having side chains 4-12 carbons in length in the copolymeric adhesive, the required balance of low tack and high cohesive strength can be imparted to the removable adhesive. One possible drawback associated with the Esmay adhesive is that its monomers may bleed through a substrate such as paper prior to curing. Such bleeding is undesirable because of the damage done to the substrate.
U.S. Pat. No. 4,737,559 (Kellen et al.) describes a PSA formulation in which the viscous flow, and resultant adhesion buildup, is controlled through the addition of a small amount of a free radically polymerizable photocrosslinker (a mono-ethylenically unsaturated aromatic ketone, most preferably 4-acryloyl-oxy-benzophenone) to at least one alkyl acrylate or methacrylate. The Kellen et al. adhesive is formulated for adhesion to skin and at times, considered to be too aggressive for paper.
U.S. Pat. No. 3,635,754 (Beede) discloses the use of a heat-activated, multi-phase pressure-sensitive adhesive copolymer whose melting point is greater than 35.degree. C. and whose glass transition temperature (T.sub.g) is below 5.degree. C. At room temperature, the adhesive is non-tacky. At that temperature, a crystalline or ordered phase and an amorphous or disordered phase co-exist. At skin temperature (approximately 35.degree. C.), the cop
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Everaerts Albert I.
Malmer Jeffrey D.
Bardell Scott A.
Griswold Gary L.
Kirn Walter N.
Lipman Bernard
Minnesota Mining and Manufacturing Company
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