Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-06-12
2003-06-17
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S101000, C525S106000, C524S267000, C428S447000
Reexamination Certificate
active
06579941
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to adhesive compositions and constructions characterized by excellent adhesion to a variety of substrates and the ability to be converted at high speeds in high-speed converting presses.
BACKGROUND OF THE INVENTION
Adhesive tapes and labels having a laminate construction are well known. In a typical construction, one or more layers of adhesive are coated on, or otherwise applied to, a release liner, and then laminated to a facestock, such as paper, polymeric film, or other flexible material. Alternatively, the adhesive is coated directly on the facestock, and the coated facestock is laminated to a release liner. The adhesive may be a pressure-sensitive adhesive (PSA), and may be rubber-based or acrylic-based. Rubber-based hot melt PSAs (HMPSAs) typically contain one or more natural or synthetic elastomers, tackified with one or more petroleum resins, rosins, or rosin derivatives, and/or other ingredients, such as plasticizers, which improve the tack of the adhesive.
PSA tape and label constructions are usually manufactured as a continuous rolls in various widths, and then passed through apparatus that converts the adhesive laminate into smaller rolls or sheets, and ultimately, individual labels and tapes. The processes involved in converting include printing, slitting, die-cutting, and matrix-stripping to leave labels on a release liner, butt-cutting of labels to the release liner, marginal hole punching, perforating, fan folding, guillotining and the like. Die-cutting involves cutting of the laminate to the surface of the release liner. Hole punching, perforating and guillotining involve cutting clean through the label laminate.
The cost of converting a laminate into a finished product is a function of the speed and efficiency at which the various processing operations occur. The faster the PSA construction can be converted, the lower the cost of the finished product. Modem converting presses are designed to be operated at speeds as high as 500 or even 1000 feet per minute, and it is desirable to manufacture PSA constrictions that can be converted at such high speeds. While the nature of all layers of the laminate can impact the cost of convertibility, the adhesive layer typically has been the greatest limiting factor in ease of convertibility. This is due to the viscoelastic nature of the adhesive, which hampers precise and clean penetration of a die in die-cutting operations and promotes adherence to die-cutting blades in shearing operations. Stringiness of the adhesive also impacts matrix-stripping operations, which follow die-cutting operations.
During guillotining or a similar shearing step, in which a plurality of label laminates are cut with a knife blade, the adhesive has a tendency to flow, either because of its general liquidity, or as a combination of that general liquidity and the exertion of pressure by the knife blade, alone or in conjunction with pressure associated with the plurality of sheets held during operation. As a result of adhesive flow during a guillotining operation, the knife blade tends to become coated with a layer of adhesive. The coating tends to reduce the efficacy of further shearing cuts, and also can deposit and smear adhesive on the edge surfaces of the articles being cut.
Adding a lubricant, such as silicone oil, wax, and/or surfactant to the PSA can reduce adhesive build-up on knife blades during shearing operations. Representative of this approach are U.S. Pat. Nos. 4,151,319 (Sackoff et al.), U.S. Pat. No. 4,346,189 (Laurent), U.S. Pat. No. 4,548,845 (Parsons), U.S. Pat. No. 5,154,974 (Norman, et al.) U.S. Pat. No 5,322,876 (Sasaki, et al.), U.S. Pat. No. 5,705,551 (Sasaki, et al.), and U.S. Pat. No. 5,939,479 (Reaves et al.). Unfortunately, most of the additives that have been tried before, although effective at reducing adhesive build-up on cutting blades, have the undesirable property of reducing the adhesivity of the PSA to which they are added. A real need exists for an improved PSA construction that exhibits both excellent adhesive performance and outstanding converting properties, especially the ability to be cleanly sheared in high-speed cutting operations.
SUMMARY OF THE INVENTION
In one aspect of the invention, an adhesive construction characterized by excellent converting performance and adhesion to a variety of substrates is provided. An adhesive laminate, preferably comprised of two or more adhesive layers, for example, a faceside adhesive (FSA) and a liner side adhesive (LSA), is coated on or laminated to a facestock. At least one adhesive layer, for example, the FSA, is compounded with a cutting aid, e.g., an organopolysiloxane or a modified organopolysiloxane. Preferably, at least one adhesive layer, for example, the LSA, is a functional PSA, i.e., an adhesive which, in dry form, is aggressively and permanently tacky at room temperature and firmly adheres to a variety of substrates upon mere contact, with no more than finger or hand pressure.
In an other aspect of the invention, an adhesive construction is comprised of a single PSA layer coated on or laminated to a facestock, the PSA being compounded with a polyalkylene oxide-modified organopolysiloxane or an ultrahigh molecular weight organopolysiloxane.
In still another aspect of the invention, improved adhesive compositions are provided. One such composition comprises an adhesive—preferably a PSA—compounded with an ultrahigh molecular weight organopolystyrene. Another adhesive composition comprises a tackified blend of elastomers compounded with an organopolysiloxane—such as an ultrahigh molecular weight organopolysiloxane dispersed in polystyrene—or a modified organopolysiloxane, such as a polyalkylene oxide-modified organopolysiloxane.
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SILWET SURFACTANTS Product Brochure; ©1997 Witco Corporation; 22 pages.
Ercillo Jesse C.
Hong Le Hoa
Sasaki Yukihiko
Avery Dennison Corporatoin
Christie Parker & Hale LLP
Moore Margaret G.
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