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
1999-12-20
2003-02-25
Wu, David W. (Department: 1713)
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...
C524S560000, C524S561000, C524S556000, C524S563000, C524S564000, C524S394000
Reexamination Certificate
active
06525129
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to water-soluble pressure-sensitive adhesives and dissolvable pressure-sensitive adhesive labels.
BACKGROUND OF THE INVENTION
Containers used in the restaurant industry typically have a label attached to indicate the content, expiration date and other necessary information. Such containers are reuseable after being cleaned. However, for reuse of the container, it is desirable that the label, including the adhesive used to attach the label to the container, be cleanly removed. Adhesive residue left on the container after washing can lead to bacteria growth. Normally such containers are passed through an industrial dishwasher, which washes at approximately 60° C. for about 30 seconds. With commercially available labels, this process frequently leaves behind adhesive residue or results in a ghosting effect, i.e., an image of the label that is stained onto the container, most likely due to migration of the adhesive into the container and the cohesive failure effect of the adhesive. The ghosting effect occurs most frequently on plastic containers. A need exists for an adhesive that can be used for such applications so that, under such washing conditions, there is no adhesive residue or ghosting effect. Additionally, the adhesive and facestock need to dissolve or break up into very small particles so that they can be eliminated with the water and not clog the dishwasher.
SUMMARY OF THE INVENTION
The present invention provides dissolvable adhesives and dissolvable adhesive label constructions that address the above concerns. The dissolvable pressure-sensitive adhesive (PSA) comprises an emulsion acrylic copolymer. The emulsion acrylic copolymer is formed from a plurality of monomers comprising at least one alkyl (meth)acrylate, at least one N-vinyl lactam monomer, and at least one hydroxy (meth)acrylate ester. In a preferred embodiment, the plurality of monomers further comprises at least one modifying monomer. In another preferred embodiment, the copolymer is blended with a post-additive to enhance the dissolvability of the PSA. Preferably the copolymer has a weight average molecular weight less than about 120,000.
In a particularly preferred embodiment, the plurality of monomers comprises at least one N-vinyl lactam monomer present in an amount ranging from about 1% to about 15% by weight, at least one hydroxy (meth)acrylate ester present in an amount ranging from about 1% to about 15% by weight, at least one alkyl (meth)acrylate present in an amount ranging from about 35% to about 80% by weight, based on the total weight of the monomers; and at least one ethylenically unsaturated carboxylic acid monomer present in an amount ranging from about 4% to about 15% by weight, based on the total weight of the monomers.
In an even more particularly preferred embodiment, the plurality of monomers comprises at least one N-vinyl lactam monomer present in an amount ranging from about 4% to about 12% by weight, at least one hydroxy (meth)acrylate ester present in an amount ranging from about 1% to about 9% by weight, at least one alkyl (meth)acrylate present in an amount ranging from about 50% to about 70% by weight, at least one ethylenically unsaturated carboxylic acid monomer present in an amount ranging from about 6% to about 12% by weight, at least one modifying monomer present in an amount ranging from about 0.05% to about 3% by weight, and at least one vinyl ester present in an amount ranging from about 11% to about 15% by weight, based on the total weight of the monomers.
In another preferred embodiment, the adhesive, when coated on a dissolvable acetate facestock and subjected to a dissolvability test (as described herein), dissolves in less than 40 seconds.
DETAILED DESCRIPTION
The present invention is directed to dissolvable pressure-sensitive adhesives (PSAs) and dissolvable PSA constructions utilizing the dissolvable PSAs. The PSA comprises an emulsion acrylic copolymer formed from a plurality of monomers comprising at least one alkyl (meth)acrylate, at least one N-vinyl lactam monomer and at least one hydroxy (meth)acrylate ester.
Examples of suitable N-vinyl lactam monomers for use in the present invention include N-vinyl-2-pyrrolidone, 5-methyl-N-vinyl-2-pyrrolidone, 5-ethyl-N-vinyl-2-pyrrolidone, 3,3-dimethyl-N-vinyl-2-pyrrolidone, 3-methyl-N-vinyl-2-pyrrolidone, 3-ethyl-N-vinyl-2-pyrrolidone, 4-methyl-N-vinyl-2-pyrrolidone, 4-ethyl-N-vinyl-2-pyrrolidone, 1-vinyl-2-piperidone, N-vinyl-2-valerolactam, N-vinyl-2-caprolactam, and mixtures thereof. The N-vinyl lactam monomer (or mixture of N-vinyl lactam monomers) is preferably present in the monomer mixture in a total amount ranging from about 1% to about 15% by weight, more preferably from about 4% to about 12% by weight, even more preferably from about 6% to about 9% by weight, based on the total weight of the monomer mixture.
Examples of suitable hydroxy (meth)acrylate esters for use in the present invention include hydroxymethyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. The hydroxy (meth)acrylate ester (or mixture of hydroxy (meth)acrylate esters) is preferably present in the monomer mixture in a total amount ranging from about 1% to about 15% by weight, more preferably from about 1% to about 9% by weight, still more preferably from about 3% to about 9% by weight, based on the total weight of the monomer mixture.
In a particularly preferred embodiment, the monomer mixture further includes a modifying monomer to increase the shear of the adhesive. The modifying monomer is selected from nitrogen-containing heterocyclic methacrylates and internal crosslinkers. An example of a suitable nitrogen-containing heterocyclic methacrylate for use in the present invention is 1-2-methacryloxyethyl)imidazolidin-2-one (commercially available in a 50/50 mix with methyl acrylate under the name Norsocryl® 104, from Elf Atochem North America, Inc., Philadelphia, Pa.). Examples of suitable internal crosslinkers include multifunctional acrylates and methacrylates, such as diacrylates (ethylene glycol diacrylate, propylene glycol diacrylate, polyethylene glycol diacrylate, and hexanediol diacrylate), dimethacrylates (ethylene glycol diacrylate, diethylene glycol dimethacrylate, and 1,3 butane glycol dimethacrylate), triacrylates (trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane triacrylate, and pentaerythritol triacrylate), and trimethacrylates (pentaerythritol trimethacrylate and trimethylolpropane trimethacrylate), as well as divinyl esters, such as divinylbenzene, divinyl succinate, divinyl adipate, divinyl maleate, divinyl oxalate, divinyl malonate, and divinyl glutarate. The modifying monomer (or mixture of modifying monomers) is preferably present in the monomer mixture in a total amount ranging from about 0.02% to about 4% by weight, more preferably from about 0.05% to about 3% by weight, based on the total weight of the monomers. If Norsocryl® 104 is used, it is preferably present in an amount ranging from about 0.1% to about 0.5% by weight, based on the total weight of the monomers.
The monomer mixture further comprises other suitable monomers typically used in the preparation of PSAs, such as alkyl (meth)acrylates, carboxylic acid monomers, vinyl esters and styrenic monomers. Examples of suitable alkyl (meth)acrylates for use in the present invention include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isobornyl acrylate, isononyl acrylate, isodecyl acrylate, methylbutyl acrylate, 4-methyl-2-pentyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate and mixtures thereof. The one or more alkyl (meth)acrylates are preferably present in the monomer mixture in a total amount ranging from about 35% to about 80% by weight, more preferably from about 50% to about 70% by weight, based on the total weight of the monomers.
Examples of su
Akeley James P.
Su Shiaonung J.
Avery Dennison Corporation
Christie Parker & Hale LLP
Lee Rip A
Wu David W.
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