Compositions – Oxidative bleachant – oxidant containing – or generative – Free halogen or oxy-halogen acid type
Reexamination Certificate
1999-05-12
2001-02-13
Anthony, Joseph D. (Department: 1721)
Compositions
Oxidative bleachant, oxidant containing, or generative
Free halogen or oxy-halogen acid type
C252S187240, C252S187250, C252S187260, C252S187330, C252S187340
Reexamination Certificate
active
06187221
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a controlled release bleach thickening composition comprising a crosslinked carboxylated polymer prepared from ethylenically unsaturated hydrophilic monomers, ethylenically unsaturated hydrophobic monomers, and a degradable crosslinking monomer having at least two ethylenically unsaturated moieties.
BACKGROUND OF THE INVENTION
Thickened aqueous bleach compositions are useful as bleaching solutions, disinfectants, hard surface cleaners and automatic dishwasher formulations. The problem with such bleach compositions, however, is that they suffer degradation and viscosity loss caused by chlorine at elevated temperatures.
Alkali soluble polyacrylate and polymethacrylate thickeners for aqueous solutions are well known. However, these have poor long term stability in alkaline, oxidative solutions such as cleaning formulations containing hypochlorite. EP 541203 describes a hypochlorite bleach containing automatic dishwashing gel thickened with CARBOPOL crosslinked polyacrylic acid. The function of the polyacrylate thickener in the gel is to expand and bind the water. U.S. Pat. No. 5,348,682 describes a CARBOPOL polyacrylic acid or ACRYSOL ICS-1 (polyEA/MAA) bleach thickening composition. EP 636689 describes a bleach composition containing a halogen or peroxy bleach material, surfactant, and a non-crosslinked polymer. The polymeric thickener is prepared from a charged hydrophilic monomer and an uncharged hydrophobic monomer. However, those skilled in the art will recognize that this formulation will not have long term stability as measured by the accelerated aging tests.
U.S. Pat. No. 5,169,552 and U.S. Pat. No. 5,384,061 describes the addition of benzoic acid or its derivatives as radical scavengers to prevent viscosity drop during accelerated aging by protecting CARBOPOL resins from oxidation by the hypochlorite. U.S. Pat. No. 4,867,896 describes CARBOPOL analogues that maintained the formulation viscosity solution by replacing the multifunctional sucrose allyl ether and pentaerythritol allyl ester crosslinkers with crosslinkers such as divinyl benzene or 1,2,4-trivinyl cyclohexane which are relatively inert to degradation by alkaline hypochlorite.
U.S. Pat. No. 4,839,077 describes the use of mixed surfactant systems to build viscosity of hypochlorite solutions wherein the addition of small amounts of ethylene/acrylic acid polymer causes a synergistic viscosity increase greater than can be obtained by surfactant thickening alone. The polymer is relatively low molecular weight, not cross-linked and has poor solubility requiring the presence of surfactants, particularly a nonionic such as amine oxide, to be soluble. These formulations have moderate heat aging stability as shown by a 50% loss in viscosity after 4 weeks at 100° F.
EP 636691 describes the use of a non-crosslinked styrene-methacrylic acid polymer to thicken hypochlorite/surfactant solutions wherein cross-linking the polymer gave higher viscosity but decreased clarity of the solution. These thickened solutions lacked long term stability loosing 50% of their viscosity after 6 weeks at room temperature.
For these reasons, there continues to be a need for a controlled release bleach thickening composition which maintains a thickening effect even at temperatures approaching 120° F. for three to four weeks.
SUMMARY OF THE INVENTION
A controlled release bleach thickening composition comprising bleach, water, and 0.1 to 50 weight percent, based on the total weight of the controlled release bleach thickening composition, of at least one crosslinked carboxylated polymer which is prepared from 30 to 80 weight percent of at least one ethylenically unsaturated hydrophilic monomer, from 20 to 70 weight percent of at least one ethylenically unsaturated hydrophobic monomer, and from about 0.5 to about 10 weight percent of a degradable crosslinking monomer selected from the group consisting of a crosslinking monomer having at least two ethylenically unsaturated moieties, a crosslinking monomer having at least one ethylenically unsaturated moiety and at least one functional group capable of reacting with another functional group on a monomer to form a degradable crosslink, and combinations thereof, wherein the weight percents are based on the total weight of monomer used to prepare the crosslinked carboxylated polymer.
In the controlled release bleach thickening composition of the invention, the solubility of the polymer is suppressed by crosslinking. Most of the polymer is isolated from degradation by the bleach, thus preventing degradation of the polymer backbone which reduces molecular weight and destroys the thickening effect. Slow but selective degradation of the polymer crosslinks acts to solubilize a small amount of polymer which functions as an efficient thickener. Once soluble, the polymer backbone will also slowly be degraded by the bleach. A continuous supply of the soluble polymer is established by this time release mechanism to replenish the soluble polymer as it is degraded by the bleach, thus maintaining the thickening effect after aging at elevated temperature for significantly longer than previously demonstrated in art.
In order to obtain a consistent viscosity over time it is preferable to have a mixture of polymers with different amounts or types of crosslinkers. Thus, the lightly crosslinked polymers provide initial viscosity while highly crosslinked polymers are less soluble and provide longer term reserves that are released more slowly.
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Gore Christopher G.
Steele Sonya M.
Anthony Joseph D.
National Starch and Chemical Investment Holding Corporation
Roland, Esq. Thomas F.
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