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
2002-12-13
2004-03-23
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S291000, C525S227000, C525S213000, C525S270000, C524S798000, C524S560000, C524S800000, C524S812000, C524S824000, C524S823000
Reexamination Certificate
active
06710128
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process to produce an aqueous composition comprising shearing a mixture to produce a mini-emulsion and polymerizing the mini-emulsion to produce the aqueous composition wherein the mixture comprises at least one tackifier, at least one ethylenically unsaturated monomer, at least one surfactant, and water. The inventive aqueous compositions are useful as adhesives, including pressure sensitive adhesives, such as, for example, tapes, labels, stickers, decals, decorative vinyls, laminates, and wall coverings.
BACKGROUND OF THE INVENTION
The production of water-based adhesives is conventionally accomplished in three basic steps. First, a latex of a vinyl polymer is prepared using emulsion polymerization processes well known in the art. In a separate step, a tackifier dispersion is prepared by combining at least one tackifier, at least one surfactant, and water and subjecting this mixture to high shear to produce a tackifier dispersion. Then, the tackifier dispersion is combined with the latex to produce an aqueous composition useful for preparation of a water-based adhesive.
Another process, which has been described in the art, involves the dissolution of a tackifier with at least one monomer in the preparation of the latex. This process avoids the tackifier dispersion step described in the previous process. However, this process is ineffective in that high scrap levels in the emulsion polymerization process can result. High scrap levels are undesirable since the yield of useful product is diminished and filtration problems can result. Therefore, there is a need for an improved process that combines tackifiers and latexes to produce an adhesive without undesirable scrap levels.
SUMMARY OF THE INVENTION
In accordance with this invention, a process to produce an aqueous composition is provided. The process comprises shearing a mixture to produce a mini-emulsion and polymerizing the mini-emulsion in the presence of an initiator to produce the aqueous composition; wherein the mixture comprises at least one tackifier, at least one ethylenically unsaturated monomer, at least one surfactant, and water.
This inventive process produces an aqueous composition that has the advantage of combining tackifiers and vinyl polymers prior to polymerizing. Therefore, the additional process step of dispersing a tackifier in the latex is not required. The invention is further advantageous in that the process uses mini-emulsion polymerization and avoids the process problems that occur when tackifiers and monomers are polymerized using conventional emulsion polymerization processes namely the production of undesirable scrap levels. The aqueous compositions are also advantaged over the art since the surfactant normally required to disperse the tackifier is not needed.
DETAILED DESCRIPTION OF THE INVENTION
A process to produce an aqueous composition is provided. The process comprises shearing a mixture to produce a mini-emulsion and polymerizing the mini-emulsion in the presence of an initiator to produce an aqueous composition. The mixture comprises at least one tackifier, at least one ethylenically unsaturated monomer, at least one surfactant, and water.
Any tackifier known in the art that can yield the properties desired in the aqueous composition can be utilized. Generally, the tackifier can be selected from the group consisting of rosins, rosin derivatives, rosin esters, hydrocarbon resins, synthetic polyterpenes, natural terpenes, and the like. More particularly, useful tackifying resins include, but are not limited to, (1) natural and modified rosins and the hydrogenated derivatives thereof; (2) esters of natural and modified rosins and the hydrogenated derivatives thereof; (3) polyterpene resins and hydrogenated polyterpene resins; (4) aliphatic petroleum hydrocarbon resins and the hydrogenated derivatives thereof; (5) aromatic hydrocarbon resins and the hydrogenated derivatives thereof; and (6) alicyclic petroleum hydrocarbon resins and the hydrogenated derivatives thereof. Mixtures of two or more of the above-described tackifiers may be required for some formulations.
Natural and modified rosins and the hydrogenated derivatives thereof include, but are not limited to, gum rosin, wood rosin, tall-oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and polymerized rosin.
Suitable examples of esters of natural and modified rosins and the hydrogenated derivatives thereof include, but are not limited to, the glycerol ester of rosin, the glycerol ester of hydrogenated rosin, the glycerol ester of polymerized rosin, the pentaerythritol ester of hydrogenated rosin.
Polyterpene resins generally result from the polymerization of terpene hydrocarbons, such as the bicyclic monoterpene known as pinene, in the presence of Friedel-Crafts catalysts at moderately low temperatures. Preferably, the polyterpene resins have a softening point, as determined by ASTM method E28-58T, of from about 80° C. to about 150° C.
Aliphatic petroleum hydrocarbon resins and hydrogenated derivatives thereof are generally produced from the polymerization of monomers consisting of primarily olefins and diolefins. Preferably, the aliphatic petroleum hydrocarbon resins have a Ball and Ring softening point of from about 70° C. to about 135° C.
Aromatic hydrocarbon resins include, for example, hydrocarbon resins derived from at least one alkyl aromatic monomer, such as, for example, styrene, alpha-methyl styrene and vinyl toluene, and the hydrogenated derivatives thereof The alkyl aromatic monomers can be obtained from petroleum distillate fractions or from non-petroleum feedstocks, such as, for example, feedstocks produced from phenol conversion processes.
An alicyclic petroleum hydrocarbon resin can be produced utilizing a hydrocarbon mixture comprising dicyclopentadiene as the monomer.
The ethylenically unsaturated monomer is at least one acrylic or vinyl monomer known in the art capable of substantially solubilizing the tackifier. The term “substantially solubilizing” means that at least 75% by weight of the tackifier should form a single-phase liquid in the ethylenically unsaturated monomer at the concentration specified. The ethylenically unsaturated monomer can be added as a single type of monomer or as a mixture. Examples of suitable ethylenically unsaturated monomers, include, but are not limited to, styrenic monomers such as, for example, styrene, &agr;-methyl styrene, vinyl naphthalene, vinyl toluene, chloromethyl styrene and the like; ethylenically unsaturated compounds such as, for example, methyl acrylate, acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, ethylhexyl acrylate, ethythexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl methacrylate, lauryl acrylate, glycidyl methacrylate, alkyl crotonates, vinyl acetate, di-n-butyl maleate, di-octylmaleate, acetoacetoxyethyl methacrylate, acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetopropryl acrylate, diacetone acrylamide, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylonitrile, and the like; and nitrogen-containing monomers, such as, for example, t-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylamide, 2-t-butylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N-(2-methacryloyloxy-ethyl)ethylene urea, and methacrylamidoethylethyiene urea.
The surfactant can be any conventional surfactant or a combination of surfactants known in the art. Generally, the surfactant is at least one selected from the group consisting of an anionic surfactant and a non-ionic surfactant. Examples of preferred surfactants include, but are not limited to, alkali alkylsulfate, ammonium alkysulfate, alkylsulfonic acid, fatty acid, oxyethylated alkyphenol, sulfosuccinates and derivatives, and mixtures thereof. A list of suitable surfactants is available in the treatise: M
Helmer Bradley James
Shoaf Glenn Lewis
Eastman Chemical Company
Graves, Jr. Bernard J.
Owen Polly C.
Sastri Satya
Wu David W.
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