Coating processes – Coating remains adhesive or is intended to be made adhesive – Pressure sensitive adhesive
Reexamination Certificate
2002-09-16
2003-08-12
Cameron, Erma (Department: 1762)
Coating processes
Coating remains adhesive or is intended to be made adhesive
Pressure sensitive adhesive
C427S385500, C427S389900, C427S394000
Reexamination Certificate
active
06605318
ABSTRACT:
This invention relates to a method for providing an improved caulk, sealant, elastomeric coating, pressure sensitive adhesive, or fabric treatment. More particularly, this invention relates to forming an aqueous composition including an aqueous acrylic emulsion polymer, the polymer including, as copolymerized units, 70 to 99.7% by weight, based on dry polymer weight, monoethylenically unsaturated nonionic (meth)acrylic monomer and from 0.3 to 10% by weight, based on dry polymer weight, monoethylenically unsaturated acid monomer, wherein the Tg of the emulsion polymer is from −90° C. to lower than −20° C., and wherein at least 40% by weight, based on dry polymer weight, of the polymer is formed by redox polymerization in the presence of 0.0005 to 0.05 moles chain transfer agent per kg dry polymer weight; applying the composition to a substrate; and drying, or allowing to dry, the applied composition.
The present invention serves to provide a caulk, sealant, elastomeric coating, pressure sensitive adhesive, or fabric treatment composition including a predominantly acrylic emulsion polymer binder of a certain composition prepared by a certain process which composition exhibits at least one improved property by which is meant herein improved relative to that of a caulk, sealant, elastomeric coating, pressure sensitive adhesive, or fabric treatment which incorporate an acrylic emulsion polymer binder not so constituted and/or prepared.
U.S. Pat. No. 5,540,987 discloses emulsion polymers including at least 50% vinyl acetate having low residual formaldehyde and providing saturated cellulosic webs having improved tensile strength. The polymers are formed by the use of an hydrophobic hydroperoxide and ascorbic acid initiator throughout the course of the reaction.
The present invention serves to provide an improved elastomeric coating, caulk, or sealant, for example improved so as to retain its integrity without cracking under stress, known in the art as crack bridging performance, even at temperatures below 0° C. Elastomeric coatings, caulks, and sealants are frequently applied to buildings and other constructions subjected to outdoor temperature extremes and desirably retain their integrity under such conditions. Also, the present invention serves to provide an improved pressure sensitive adhesive having improved tack which may be desirable in itself or, alternatively, may provide the basis for adjustment of the other adhesives properties such as, for example, the tack/shear balance at an acceptable level of tack. And, the present invention serves to provide an improved fabric treatment. By “fabric treatment” herein is meant, for example, a woven or nonwoven fabric coating, binder (as saturation binder), or adhesive coating (as flocking adhesive).
We have now found that that certain predominantly acrylic emulsion polymer compositions having a Tg of the emulsion polymer from −90° C. to lower than −20° C. prepared wherein at least 40% by weight, based on dry polymer weight, of the emulsion polymer is formed by redox polymerization in the presence of 0.0005 to 0.05 moles chain transfer agent per kg dry polymer provide an improved caulk, sealant, elastomeric coating, pressure sensitive adhesive, or fabric treatment provide at least one improved property.
In a first aspect of the present invention there is provided a method for providing a caulk, sealant, elastomeric coating, pressure sensitive adhesive, or fabric treatment comprising: forming an aqueous composition comprising an aqueous acrylic emulsion polymer, said polymer comprising, as copolymerized units, 70 to 99.7% by weight, based on dry polymer weight, monoethylenically unsaturated nonionic (meth)acrylic monomer and from 0.3 to 10% by weight, based on dry polymer weight, monoethylenically unsaturated acid monomer, wherein the Tg of said emulsion polymer is from −90° C. to lower than −20° C., and wherein at least 40% by weight, based on dry polymer weight, of said polymer is formed by redox polymerization in the presence of 0.0005 to 0.05 moles chain transfer agent per kg dry polymer weight; applying said aqueous composition to a substrate; and drying, or allowing to dry, said applied aqueous composition.
The aqueous acrylic emulsion polymer contains, as copolymerized units, 70 to 99.7% by weight, based on dry polymer weight, monoethylenically-unsaturated nonionic (meth)acrylic monomer including esters, amides, and nitriles of (meth)acrylic acid, such as, for example, (meth)acrylic ester monomer including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, aminoalkyl (meth)acrylate, N-alkyl aminoalkyl (meth)acrylate, N,N-dialkyl aminoalkyl (meth)acrylate; urieido (meth)acrylate; (meth)acrylonitrile and (meth)acrylamide. The use of the term “(meth)” followed by another term such as acrylate, acrylonitrile, or acrylamide, as used throughout the disclosure, refers to both acrylate, acrylonitrile, or acrylamide and methacrylate, methacrylonitrile, and methacrylamide, respectively. By “nonionic monomer” herein is meant that the copolymerized monomer residue does not bear an ionic charge between pH=1-14.
The aqueous acrylic emulsion polymer contains, as copolymerized units, from 0.3 to 10% by weight, based on dry polymer weight, monoethylenically-unsaturated acid monomer such as, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, sulfoethyl methacrylate, phosphoethyl methacrylate, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride. Preferably, the emulsion polymer contains, as copolymerized units, from 0.3 to 2.5% by weight, based on dry polymer weight, (meth)acrylic acid.
The aqueous acrylic emulsion polymer further contains, as copolymerized units, from 0 to 29.4% by weight, based on dry polymer weight, of optional monomers which are neither nonionic monoethylenically-unsaturated nonionic (meth)acrylic monomers nor monoethylenically-unsaturated acid monomers. However, the amount of multiethylenically unsaturated monomers must not exceed, as copolymerized units, 1% by weight, based on dry polymer weight. Optional monomers may include, for example, styrene or alkyl-substituted styrenes; butadiene; vinyl acetate, vinyl propionate, or other vinyl esters; vinyl monomers such as vinyl chloride, vinylidene chloride, and N-vinyl pyrollidone; allyl methacrylate, vinyl toluene, vinyl benzophenone, diallyl phthalate, 1,3-butylene glycol dimethacrylate, 1,6-hexanedioldiacrylate, and divinyl benzene.
The aqueous acrylic emulsion polymer used in this invention is substantially uncrosslinked, when it is applied to a substrate in the method of this invention, although low levels of deliberate or adventitious crosslinking may be present. When low levels of precrosslinking or gel content are desired low levels of optional nonionic multi-ethylenically unsaturated monomers such as, for example, 0.1%-1%, by weight based on the dry polymer weight, may be used. It is important, however, that the quality of the film formation is not materially impaired.
The aqueous acrylic emulsion polymer of this invention is prepared by emulsion polymerization as is well known in the art. Conventional surfactants may be used such as, for example, anionic and/or nonionic emulsifiers such as, for example, alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols. The amount of surfactant used is usually 0.1% to 6% by weight, based on the weight of monomer.
A redox initiation system is used. The redox system includes an oxidant and a reductant. One or more oxidants such as, for example, hydrogen peroxide, sodium peroxide, potassium peroxide; t-alkyl hydroperoxide, t-alkyl peroxide, or t-alkyl perester wherein th
Even Ralph Craig
Slone Robert Victor
Bakule Ronald D.
Cameron Erma
Rohm and Haas Company
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